After Kwan spent $5 of the money he earned for mowing lawns, he had $15 left. Which equation represents how to find the amount Kwan had before spending the money?

$20 was how much money he had before he spent any money.

Step-by-step explanation:

So, with any problem like this, all you have to do to figure out the answer is to add how much money is left and how much was spent. So, like this:

Amount left + Amount spent = Original Amount