Let's roll up our sleeves and solve this. We have 138 and we're going to multiply it by 6, essentially adding 138 to itself 6 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
Step 6: 690 + 138 = 828

So, 138*6 = 828