Scott spends $250 for a lawn mower but earns $25 a week mowing lawns. how much profit will he a have after 20 weeks

25 (a week mowing lawns) multiplied by 20 (weeks)
25 x 20 = 500 (profit total without subtracting lawn mower)
500 - 250 (lawn mower) = 250 profit for 20 weeks.
If Scott spends another 20 weeks, he would gain 500 profit total, because the price of the lawn mower is one time.

If ScoTT earns $25 per week
$25*20 = $500

but due to the initial investment, the final earns will be 
$500 - $250 = $250

The percent increase is 25%