Please help me answer this question

Find the missing dimension! need asap! tiny square is a =3025 in ²

3.4a=57.8 what is the the value of a

Tony is charged $ 50 and additional $0.15 per miles for renting a car. a) represent the cost of renting a car with an equation,and the determine the cost if he drove it70 miles.b) what would be the cost of a car rental if the car was driven 250 miles? show work