"FIVE PERCENT OFF"

This is one of the most straightforward percentage calculations you'll ever do.

Let's say you've got a 50 cent candy bar and it's 5% off. You can look at this one of two ways - either you're paying 95% or you're getting back 5% as change.
 

0.50 * 0.95 = 0.47
0.50 * 0.05 =  0.03
It's also worth noting that the fact that .47 + .03 is equal to the original purchase price of your candy bar (0.50) is no coincidence.

If you were getting five percent off of the $200,000 house,

0.05 * $200,000 = $10,000