OK, let's crack this. We're given 642 and our task is to multiply it by 9. Essentially, we'll be adding 642 to itself 9 times.
Step 1: 0 + 642 = 642
Step 2: 642 + 642 = 1284
Step 3: 1284 + 642 = 1926
Step 4: 1926 + 642 = 2568
Step 5: 2568 + 642 = 3210
Step 6: 3210 + 642 = 3852
Step 7: 3852 + 642 = 4494
Step 8: 4494 + 642 = 5136
Step 9: 5136 + 642 = 5778

So, 642*9 = 5778