Answer:
let
m = the speed of Mattie
d1 = 180 mi the distance Mattie traveled
p = the speed of the plane
d2 = 630 mi the distance the plane traveled
the speed of the plane was 150 mph faster than the speed of the car
p = m + 150
since speed = distance/time => time = distance/speed
d1/m = d2/p
180/m = 630/p cross multiply
180p = 630m divide both sides by 90
2p = 7m
by solving the system of equations
p = m + 150
2p = 7m
we find
p = 210 mph
The speed of the plane was 210 mph