Without delay, let's solve this. We've got 842 and we will be multiplying it by 30, that is, adding 842 to itself 30 times.
Step 1: 0 + 842 = 842
Step 2: 842 + 842 = 1684
Step 3: 1684 + 842 = 2526
Step 4: 2526 + 842 = 3368
Step 5: 3368 + 842 = 4210
Step 6: 4210 + 842 = 5052
Step 7: 5052 + 842 = 5894
Step 8: 5894 + 842 = 6736
Step 9: 6736 + 842 = 7578
Step 10: 7578 + 842 = 8420
Step 11: 8420 + 842 = 9262
Step 12: 9262 + 842 = 10104
Step 13: 10104 + 842 = 10946
Step 14: 10946 + 842 = 11788
Step 15: 11788 + 842 = 12630
Step 16: 12630 + 842 = 13472
Step 17: 13472 + 842 = 14314
Step 18: 14314 + 842 = 15156
Step 19: 15156 + 842 = 15998
Step 20: 15998 + 842 = 16840
Step 21: 16840 + 842 = 17682
Step 22: 17682 + 842 = 18524
Step 23: 18524 + 842 = 19366
Step 24: 19366 + 842 = 20208
Step 25: 20208 + 842 = 21050
Step 26: 21050 + 842 = 21892
Step 27: 21892 + 842 = 22734
Step 28: 22734 + 842 = 23576
Step 29: 23576 + 842 = 24418
Step 30: 24418 + 842 = 25260

So, 842*30 = 25260