Flying to miami whit a tailwind a plane averaged 376 mph. on the return trip the plane only averaged 312 mph while flying back into the same wind. find the speed of the wind and speed of the plane in still air. show me the work

Let x =  the speed of the plane, mph
Let y =  the speed of the wind., mph

When flying with a tailwind, the effective speed of the plane is (x + y), therefore
x + y = 376         (1)

When flying back against the wind, the effective speed is (x-y), therefore
x - y = 312           (2)

Add (1) and (2).
2x = 376+312 = 688
x = 344 mph
y = 376 - x = 32

Plane: 344 mph
Wind: 32 mph