Let's get this math done. We have 729 and we're going to multiply it by 7. This is the same as taking 729 and adding it to itself 7 times.
Step 1: 0 + 729 = 729
Step 2: 729 + 729 = 1458
Step 3: 1458 + 729 = 2187
Step 4: 2187 + 729 = 2916
Step 5: 2916 + 729 = 3645
Step 6: 3645 + 729 = 4374
Step 7: 4374 + 729 = 5103

So, 729*7 = 5103