Let's get this math done. We have 138 and we're going to multiply it by 5. This is the same as taking 138 and adding it to itself 5 times.
Step 1: 0 + 138 = 138
Step 2: 138 + 138 = 276
Step 3: 276 + 138 = 414
Step 4: 414 + 138 = 552
Step 5: 552 + 138 = 690

So, 138*5 = 690