Answer:
i think this
Explanation:
Let Va = the velocity of the airplane
Let Vw = the velocity of the wind
When flying with the wind:
(Va+Vw)*(4 hours) = 4000
4Va + 4Vw = 4000
4Vw = 4000 - 4Va
Vw = 1000 - Va
When flying against the wind:
(Va-Vw)*(7 hours) = 4200 km
7Va - 7Vw = 4200
Substitute 1000-Va for Vw and solve for Va:
7Va - 7(1000-Va) = 4200
7Va -7000 + 7Va = 4200
14Va = 11200
Va = 800 km/hr
Rate of wind:
Vw = 1000 - Va = 1000 - 800 = 200 km/hour