6 × 22 = 8 × ( s - w ) ; and s + w = 22 ; where s = the speed of the plane in still air and w = the speed of the wind ;
132 = 8 × ( s - w );
s - w = 16,5 km/h;
s+ w = 22 km/h
----------------------------------( + )
2s = 38,5 km/h;
s = 38,5÷2;
s = 19,25 km/h ;
