Virginia's Painting service charges $10 per job and $0.20 per square foot. If virginia earned $50 for painting one job, how many square feet did she paint at the job?

We are told that the total charge for the job was $50,

so we have all we need for finding x (# of square feet):

10 + 0.20x = 50

Solving for x:

0.20x = 50 - 10

0.20x = 40

x = 40/0.20

x = 200 square feet