Jacks plane will normally cover 52 km in 12 min in still air. on one trip, he flew with the wind for 2.5h. returning, he still had 100km to go after 3.5h. what was the wind speed?

  60 kph

Step-by-step explanation:

The relation between time, speed, and distance is ...

  time = distance/speed

  speed = distance/time

  distance = speed × time

___

Jack's plane flies at a speed of ...

  (52 km)/(0.2 h) = 260 km/h

If the wind speed is represented by w in km/h, then the distance remaining (in km) is ...

  (distance there) - (distance covered in 3.5 h) = 100 km

  (260 +w)(2.5) - (260 -w)(3.5) = 100

  -260 +6w = 100

  6w = 360

  w = 60

The wind speed was 60 km/h.

Check

The distance going was ...

  ((260 +60) km/h)(2.5 h) = 800 km

The distance covered in 3.5 hours coming back was ...

  ((260 -60) km/h)(3.5 h) = 700 km . . . . . 100 km short of the destination