Robin flies to San Francisco from LA in 4 hours. she flies back in 3 hours. if the wind is blowing from the north at velocity of 20mph during both flights, what was the airspeed of the plane (it's speed in the air)?

Answer 1

since distance = speed * time

4(s-20) = 3(s+20)

and we know what airspeed: it's its speed in the air. (note apostrophe)

Answer 2

I think we are to assume that San Francisco is just about north of LA

airspeed of plane ---- x mph
speed from SF to LA --- x + 20
speed from LA to SF ---- x - 20

distance one way = 4(x-20)
distance the other way = 3(x+20)
same distance, so

4x - 80 = 3x + 60
x = 140

speed of plane was only 140 mph ???

check:
4(120) =480
3(160) = 480