An airplane takes 3 hours to travel a distance of 1680 miles with the wind. The return trip was 4 hours against wind. Find the speed of the plane in still air and the speed of the wind

Speed of plane in still air: 490  mile/hour

speed of wind: 70  mile/hour

Step-by-step explanation:

still speed = x        wind speed = w

with wind: speed = still + wind

(x+w) * 3 = 1680     ...a

against wind: speed = still - wind

(x-w) * 4 = 1680    ...b

b-a ... 4x-4w-3x-3w = 0

x-7w = 0

x = 7w

substitution: (7w+w)*3 = 1680      8w = 560       wind speed (w) = 70

still speed (x) = 7w = 490 mile/hour

answer:   b

step-by-step explanation:

x2 = 16

x can not be a negative number because 16 is positive

the only answer would be positive 8  

step-by-step explanation:

for exempl this   system of equations   y = x - 3

                                                                y = 2x - 5

look   the line : y = x -3     ( red)

                            the line : y = 2x -5 ( bleus)