#### Answer

800 miles

#### Work Step by Step

The cost for the weekly rental is represented by the formula $200+0.15x$, where x is the number of miles driven.
Solve for x when the rental charge is 320.
$320=200+0.15x$
Use the addition property of equality to subtract 200 from each side of the equation.
$320-200=200+0.15x-200$
Simplify.
$120=0.15x$
Use the multiplication property of equality to divide each side of the equation by 0.15.
$120\div0.15=0.15x\div0.15$
Simplify.
$800=x$