Question 948147

When a plane flies into the wind , it can travel 3000km in 6 hours. When it flies with the wind, it can travel the same distance in 5 hours. Find the rate of the plane in still air and the rate of the wind. 

I sorta know how to do these problems. I am just a little confused on this one. Could you help me with this one please?
<pre>
Let speed of plane in still air, be S, and speed of wind, W
Average speed when flying against wind: {{{3000/6}}}, or 500 km
Average speed when flying with wind: {{{3000/5}}}, or 600 km
Speed of plane in still air, less wind’s speed, equals average speed against wind, OR
S – W = 500 -------- eq (i)
Speed of plane in still air, plus wind’s speed, equals average speed with wind, OR
S + W = 600 -------- eq (ii)
2S = 1,100 -------- Adding eqs (ii) & (i)
S, or speed of plane in still air = {{{1100/2}}}, or {{{highlight_green(550)}}} km/h
550 – W = 500 -------- Substituting 550 for S in eq (i) 
- W = 500 – 550 
- W = - 50
W, or speed of wind = {{{(- 50)/(- 1)}}}, or {{{highlight_green(50)}}} km/h