OK, let's crack this. We're given 156 and our task is to multiply it by 15. Essentially, we'll be adding 156 to itself 15 times.
Step 1: 0 + 156 = 156
Step 2: 156 + 156 = 312
Step 3: 312 + 156 = 468
Step 4: 468 + 156 = 624
Step 5: 624 + 156 = 780
Step 6: 780 + 156 = 936
Step 7: 936 + 156 = 1092
Step 8: 1092 + 156 = 1248
Step 9: 1248 + 156 = 1404
Step 10: 1404 + 156 = 1560
Step 11: 1560 + 156 = 1716
Step 12: 1716 + 156 = 1872
Step 13: 1872 + 156 = 2028
Step 14: 2028 + 156 = 2184
Step 15: 2184 + 156 = 2340

So, 156*15 = 2340