Solve
-A Plane Flies 420 Miles with the Wind and 350

Multiple Choice

Solve.
-A plane flies 420 miles with the wind and 350 miles against the wind in the same length of time. If the speed of the wind is $21 \mathrm { mph }$ , what is the speed of the plane in still air?

A) $256 \mathrm { mph }$
B) $236 \mathrm { mph }$
C) $231 \mathrm { mph }$
D) $221 \mathrm { mph }$