Let's get this math done. We have 396 and we're going to multiply it by 42. This is the same as taking 396 and adding it to itself 42 times.
Step 1: 0 + 396 = 396
Step 2: 396 + 396 = 792
Step 3: 792 + 396 = 1188
Step 4: 1188 + 396 = 1584
Step 5: 1584 + 396 = 1980
Step 6: 1980 + 396 = 2376
Step 7: 2376 + 396 = 2772
Step 8: 2772 + 396 = 3168
Step 9: 3168 + 396 = 3564
Step 10: 3564 + 396 = 3960
Step 11: 3960 + 396 = 4356
Step 12: 4356 + 396 = 4752
Step 13: 4752 + 396 = 5148
Step 14: 5148 + 396 = 5544
Step 15: 5544 + 396 = 5940
Step 16: 5940 + 396 = 6336
Step 17: 6336 + 396 = 6732
Step 18: 6732 + 396 = 7128
Step 19: 7128 + 396 = 7524
Step 20: 7524 + 396 = 7920
Step 21: 7920 + 396 = 8316
Step 22: 8316 + 396 = 8712
Step 23: 8712 + 396 = 9108
Step 24: 9108 + 396 = 9504
Step 25: 9504 + 396 = 9900
Step 26: 9900 + 396 = 10296
Step 27: 10296 + 396 = 10692
Step 28: 10692 + 396 = 11088
Step 29: 11088 + 396 = 11484
Step 30: 11484 + 396 = 11880
Step 31: 11880 + 396 = 12276
Step 32: 12276 + 396 = 12672
Step 33: 12672 + 396 = 13068
Step 34: 13068 + 396 = 13464
Step 35: 13464 + 396 = 13860
Step 36: 13860 + 396 = 14256
Step 37: 14256 + 396 = 14652
Step 38: 14652 + 396 = 15048
Step 39: 15048 + 396 = 15444
Step 40: 15444 + 396 = 15840
Step 41: 15840 + 396 = 16236
Step 42: 16236 + 396 = 16632

So, 396*42 = 16632