Answer:
System of equation: 0.75(x+y)=120 and x-y=120
A is correct
Explanation:
An aircraft travels with the wind for 120 miles in 0.75 of an hour.
The return trip is flown against the wind and takes exactly 1 hour.
Let speed of aircraft be x mph and speed of wind y mph
Formula:

Case 1: When aircraft along with wind
Speed = x+y
Time = 0.75
Distance = 120


0.75(x+y)=120
Case 2: When aircraft against with wind
Speed = x-y
Time = 1
Distance = 120

x-y=120
Hence, The system of equation are 0.75(x+y)=120 and x-y=120