math
posted by meep .
Maria normally spends a halfhour driving to work. When her average speed is ten miles per hour slower than usual, the trip takes ten minutes longer. How many miles does she drive to work?

s*(1/2) = (s10)(1/2 + 1/6)
s = 40
check:
40mi/hr * 1/2 hr = 20 mi
30mi/hr * 2/3 hr = 20 mi