Let's get this math done. We have 72 and we're going to multiply it by 9. This is the same as taking 72 and adding it to itself 9 times.
Step 1: 0 + 72 = 72
Step 2: 72 + 72 = 144
Step 3: 144 + 72 = 216
Step 4: 216 + 72 = 288
Step 5: 288 + 72 = 360
Step 6: 360 + 72 = 432
Step 7: 432 + 72 = 504
Step 8: 504 + 72 = 576
Step 9: 576 + 72 = 648

So, 72*9 = 648