Let's roll up our sleeves and solve this. We have 31 and we're going to multiply it by 5, essentially adding 31 to itself 5 times.
Step 1: 0 + 31 = 31
Step 2: 31 + 31 = 62
Step 3: 62 + 31 = 93
Step 4: 93 + 31 = 124
Step 5: 124 + 31 = 155

So, 31*5 = 155