Let's get this math done. We have 123 and we're going to multiply it by 10. This is the same as taking 123 and adding it to itself 10 times.
Step 1: 0 + 123 = 123
Step 2: 123 + 123 = 246
Step 3: 246 + 123 = 369
Step 4: 369 + 123 = 492
Step 5: 492 + 123 = 615
Step 6: 615 + 123 = 738
Step 7: 738 + 123 = 861
Step 8: 861 + 123 = 984
Step 9: 984 + 123 = 1107
Step 10: 1107 + 123 = 1230

So, 123*10 = 1230