Solve the Problem $25 \mathrm{mph}$ , What Is the Speed of the Plane in Still

Multiple Choice

Solve the problem.
-A plane flies 420 miles with the wind and 300 miles against the wind in the same length of time. If the speed of the wind is $25 \mathrm{mph}$ , what is the speed of the plane in still air?

A) $175 \mathrm{mph}$
B) $140 \mathrm{mph}$
C) $155 \mathrm{mph}$
D) $150 \mathrm{mph}$