Let's roll up our sleeves and solve this. We have 149 and we're going to multiply it by 20, essentially adding 149 to itself 20 times.
Step 1: 0 + 149 = 149
Step 2: 149 + 149 = 298
Step 3: 298 + 149 = 447
Step 4: 447 + 149 = 596
Step 5: 596 + 149 = 745
Step 6: 745 + 149 = 894
Step 7: 894 + 149 = 1043
Step 8: 1043 + 149 = 1192
Step 9: 1192 + 149 = 1341
Step 10: 1341 + 149 = 1490
Step 11: 1490 + 149 = 1639
Step 12: 1639 + 149 = 1788
Step 13: 1788 + 149 = 1937
Step 14: 1937 + 149 = 2086
Step 15: 2086 + 149 = 2235
Step 16: 2235 + 149 = 2384
Step 17: 2384 + 149 = 2533
Step 18: 2533 + 149 = 2682
Step 19: 2682 + 149 = 2831
Step 20: 2831 + 149 = 2980

So, 149*20 = 2980