Set this up as a ratio putting inches on top and feet on bottom. Then your first ratio would be 1/25 since 1 inch is the same as 25 feet. In between them goes an equals sign and the the other ratio has an x on top (because inches is what we are looking for) and the 1500 on the bottom. Cross multiply to solve for x:
1(1500) = x(25). Divide both sides by 25 to get 60
284 x $1.39= $394.76
He made $394.76 washing 284 windows last week
The slope is either 5/2 or 2/5 and the y intercept is 3