.
Let u be the average speed flying with the wind (in km/h), and
let v be the average speed flying into the wind.
Then from the condition
u + v = 306 (1)
u - v = 238 (2)
Add the equation and get u
2u = 306 + 238 = 544, u = 544/2 = 272.
Then from equation (1),
272 + v = 306, v = 306 - 272 = 34.
ANSWER. The speed of the plane in still are is 272 km/h; the speed of the wind is 34 km/h.
Solved.