How do find points on a graph

Solve the formula ax+ by = c for x.

Five friends found a dollar on the ground and decided they each should get 1/5 of it. what amount of money will each friend get? $0.05 $0.20 $0.30 $0.80

Ashley spent half of her lunch money on a turkey sandwich. then she spent two-thirds of the money she had left on a bottle of juice and the rest of the money on a cookie. if the cookie cost $.75, how much lunch money did ashley have to start with?