Sure thing! We've got 126 and we're gonna multiply it by 15. That's the same as adding 126 to itself 15 times.
Step 1: 0 + 126 = 126
Step 2: 126 + 126 = 252
Step 3: 252 + 126 = 378
Step 4: 378 + 126 = 504
Step 5: 504 + 126 = 630
Step 6: 630 + 126 = 756
Step 7: 756 + 126 = 882
Step 8: 882 + 126 = 1008
Step 9: 1008 + 126 = 1134
Step 10: 1134 + 126 = 1260
Step 11: 1260 + 126 = 1386
Step 12: 1386 + 126 = 1512
Step 13: 1512 + 126 = 1638
Step 14: 1638 + 126 = 1764
Step 15: 1764 + 126 = 1890

So, 126*15 = 1890