Let's roll up our sleeves and solve this. We have 142 and we're going to multiply it by 15, essentially adding 142 to itself 15 times.
Step 1: 0 + 142 = 142
Step 2: 142 + 142 = 284
Step 3: 284 + 142 = 426
Step 4: 426 + 142 = 568
Step 5: 568 + 142 = 710
Step 6: 710 + 142 = 852
Step 7: 852 + 142 = 994
Step 8: 994 + 142 = 1136
Step 9: 1136 + 142 = 1278
Step 10: 1278 + 142 = 1420
Step 11: 1420 + 142 = 1562
Step 12: 1562 + 142 = 1704
Step 13: 1704 + 142 = 1846
Step 14: 1846 + 142 = 1988
Step 15: 1988 + 142 = 2130

So, 142*15 = 2130