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.