Let's get this math done. We have 789 and we're going to multiply it by 17. This is the same as taking 789 and adding it to itself 17 times.
Step 1: 0 + 789 = 789
Step 2: 789 + 789 = 1578
Step 3: 1578 + 789 = 2367
Step 4: 2367 + 789 = 3156
Step 5: 3156 + 789 = 3945
Step 6: 3945 + 789 = 4734
Step 7: 4734 + 789 = 5523
Step 8: 5523 + 789 = 6312
Step 9: 6312 + 789 = 7101
Step 10: 7101 + 789 = 7890
Step 11: 7890 + 789 = 8679
Step 12: 8679 + 789 = 9468
Step 13: 9468 + 789 = 10257
Step 14: 10257 + 789 = 11046
Step 15: 11046 + 789 = 11835
Step 16: 11835 + 789 = 12624
Step 17: 12624 + 789 = 13413

So, 789*17 = 13413