Sure thing, let's get straight to it. We start with 129 and we're going to multiply it by 10, which means adding 129 to itself 10 times.
Step 1: 0 + 129 = 129
Step 2: 129 + 129 = 258
Step 3: 258 + 129 = 387
Step 4: 387 + 129 = 516
Step 5: 516 + 129 = 645
Step 6: 645 + 129 = 774
Step 7: 774 + 129 = 903
Step 8: 903 + 129 = 1032
Step 9: 1032 + 129 = 1161
Step 10: 1161 + 129 = 1290

So, 129*10 = 1290