Let's roll up our sleeves and solve this. We have 999 and we're going to multiply it by 150, essentially adding 999 to itself 150 times.
Step 1: 0 + 999 = 999
Step 2: 999 + 999 = 1998
Step 3: 1998 + 999 = 2997
Step 4: 2997 + 999 = 3996
Step 5: 3996 + 999 = 4995
Step 6: 4995 + 999 = 5994
Step 7: 5994 + 999 = 6993
Step 8: 6993 + 999 = 7992
Step 9: 7992 + 999 = 8991
Step 10: 8991 + 999 = 9990
Step 11: 9990 + 999 = 10989
Step 12: 10989 + 999 = 11988
Step 13: 11988 + 999 = 12987
Step 14: 12987 + 999 = 13986
Step 15: 13986 + 999 = 14985
Step 16: 14985 + 999 = 15984
Step 17: 15984 + 999 = 16983
Step 18: 16983 + 999 = 17982
Step 19: 17982 + 999 = 18981
Step 20: 18981 + 999 = 19980
Step 21: 19980 + 999 = 20979
Step 22: 20979 + 999 = 21978
Step 23: 21978 + 999 = 22977
Step 24: 22977 + 999 = 23976
Step 25: 23976 + 999 = 24975
Step 26: 24975 + 999 = 25974
Step 27: 25974 + 999 = 26973
Step 28: 26973 + 999 = 27972
Step 29: 27972 + 999 = 28971
Step 30: 28971 + 999 = 29970
Step 31: 29970 + 999 = 30969
Step 32: 30969 + 999 = 31968
Step 33: 31968 + 999 = 32967
Step 34: 32967 + 999 = 33966
Step 35: 33966 + 999 = 34965
Step 36: 34965 + 999 = 35964
Step 37: 35964 + 999 = 36963
Step 38: 36963 + 999 = 37962
Step 39: 37962 + 999 = 38961
Step 40: 38961 + 999 = 39960
Step 41: 39960 + 999 = 40959
Step 42: 40959 + 999 = 41958
Step 43: 41958 + 999 = 42957
Step 44: 42957 + 999 = 43956
Step 45: 43956 + 999 = 44955
Step 46: 44955 + 999 = 45954
Step 47: 45954 + 999 = 46953
Step 48: 46953 + 999 = 47952
Step 49: 47952 + 999 = 48951
Step 50: 48951 + 999 = 49950
Step 51: 49950 + 999 = 50949
Step 52: 50949 + 999 = 51948
Step 53: 51948 + 999 = 52947
Step 54: 52947 + 999 = 53946
Step 55: 53946 + 999 = 54945
Step 56: 54945 + 999 = 55944
Step 57: 55944 + 999 = 56943
Step 58: 56943 + 999 = 57942
Step 59: 57942 + 999 = 58941
Step 60: 58941 + 999 = 59940
Step 61: 59940 + 999 = 60939
Step 62: 60939 + 999 = 61938
Step 63: 61938 + 999 = 62937
Step 64: 62937 + 999 = 63936
Step 65: 63936 + 999 = 64935
Step 66: 64935 + 999 = 65934
Step 67: 65934 + 999 = 66933
Step 68: 66933 + 999 = 67932
Step 69: 67932 + 999 = 68931
Step 70: 68931 + 999 = 69930
Step 71: 69930 + 999 = 70929
Step 72: 70929 + 999 = 71928
Step 73: 71928 + 999 = 72927
Step 74: 72927 + 999 = 73926
Step 75: 73926 + 999 = 74925
Step 76: 74925 + 999 = 75924
Step 77: 75924 + 999 = 76923
Step 78: 76923 + 999 = 77922
Step 79: 77922 + 999 = 78921
Step 80: 78921 + 999 = 79920
Step 81: 79920 + 999 = 80919
Step 82: 80919 + 999 = 81918
Step 83: 81918 + 999 = 82917
Step 84: 82917 + 999 = 83916
Step 85: 83916 + 999 = 84915
Step 86: 84915 + 999 = 85914
Step 87: 85914 + 999 = 86913
Step 88: 86913 + 999 = 87912
Step 89: 87912 + 999 = 88911
Step 90: 88911 + 999 = 89910
Step 91: 89910 + 999 = 90909
Step 92: 90909 + 999 = 91908
Step 93: 91908 + 999 = 92907
Step 94: 92907 + 999 = 93906
Step 95: 93906 + 999 = 94905
Step 96: 94905 + 999 = 95904
Step 97: 95904 + 999 = 96903
Step 98: 96903 + 999 = 97902
Step 99: 97902 + 999 = 98901
Step 100: 98901 + 999 = 99900
Step 101: 99900 + 999 = 100899
Step 102: 100899 + 999 = 101898
Step 103: 101898 + 999 = 102897
Step 104: 102897 + 999 = 103896
Step 105: 103896 + 999 = 104895
Step 106: 104895 + 999 = 105894
Step 107: 105894 + 999 = 106893
Step 108: 106893 + 999 = 107892
Step 109: 107892 + 999 = 108891
Step 110: 108891 + 999 = 109890
Step 111: 109890 + 999 = 110889
Step 112: 110889 + 999 = 111888
Step 113: 111888 + 999 = 112887
Step 114: 112887 + 999 = 113886
Step 115: 113886 + 999 = 114885
Step 116: 114885 + 999 = 115884
Step 117: 115884 + 999 = 116883
Step 118: 116883 + 999 = 117882
Step 119: 117882 + 999 = 118881
Step 120: 118881 + 999 = 119880
Step 121: 119880 + 999 = 120879
Step 122: 120879 + 999 = 121878
Step 123: 121878 + 999 = 122877
Step 124: 122877 + 999 = 123876
Step 125: 123876 + 999 = 124875
Step 126: 124875 + 999 = 125874
Step 127: 125874 + 999 = 126873
Step 128: 126873 + 999 = 127872
Step 129: 127872 + 999 = 128871
Step 130: 128871 + 999 = 129870
Step 131: 129870 + 999 = 130869
Step 132: 130869 + 999 = 131868
Step 133: 131868 + 999 = 132867
Step 134: 132867 + 999 = 133866
Step 135: 133866 + 999 = 134865
Step 136: 134865 + 999 = 135864
Step 137: 135864 + 999 = 136863
Step 138: 136863 + 999 = 137862
Step 139: 137862 + 999 = 138861
Step 140: 138861 + 999 = 139860
Step 141: 139860 + 999 = 140859
Step 142: 140859 + 999 = 141858
Step 143: 141858 + 999 = 142857
Step 144: 142857 + 999 = 143856
Step 145: 143856 + 999 = 144855
Step 146: 144855 + 999 = 145854
Step 147: 145854 + 999 = 146853
Step 148: 146853 + 999 = 147852
Step 149: 147852 + 999 = 148851
Step 150: 148851 + 999 = 149850

So, 999*150 = 149850