Let's roll up our sleeves and solve this. We have 665 and we're going to multiply it by 4, essentially adding 665 to itself 4 times.
Step 1: 0 + 665 = 665
Step 2: 665 + 665 = 1330
Step 3: 1330 + 665 = 1995
Step 4: 1995 + 665 = 2660

So, 665*4 = 2660