98) Flying to Madrid with a tailwind a plane averaged $315 \mathrm{~km} / \mathrm{h}$. On the return trip the plane only averaged $243 \mathrm{~km} / \mathrm{h}$ while flying back into the same wind. Find the speed of the wind and the speed of the plane in still air.

Step 1 ：Let's denote the speed of the plane in still air as p and the speed of the wind as w.

Step 2 ：When the plane is flying to Madrid with a tailwind, the speed of the plane and the speed of the wind add up. So, we can write this as an equation: \(p + w = 315\) km/h.

Step 3 ：On the return trip, the plane is flying into the wind, so the speed of the wind is subtracted from the speed of the plane. We can write this as another equation: \(p - w = 243\) km/h.

Step 4 ：We can solve these two equations simultaneously to find the values of p and w.

Step 5 ：The solution to the system of equations is {p: 279, w: 36}. This means that the speed of the plane in still air is 279 km/h and the speed of the wind is 36 km/h.

Step 6 ：Final Answer: The speed of the plane in still air is \(\boxed{279 \mathrm{~km/h}}\) and the speed of the wind is \(\boxed{36 \mathrm{~km/h}}\).