Problem Solving

Last year the annual premium on a certain hospitalization insurance policy was $408, and the policy paid 80 percent of any hospital expenses incurred. If the amount paid by the insurance policy last year was equal to the annual premium plus the amount of hospital expenses not paid by the policy, what was the total amount of hospital expenses last year?
$850.00
$680.00
$640.00
$510.00
$326.40

The ans is B, how to solve it?

Assume total amount of hospital expenses last year = x
so total amount paid = 0.8x
which is also = 408 + 0.2x

so solve for 408 + 0.2x = 0.8x