Answer:his speed in still air is 6 miles per minute.
the speed of the wind is 1 mile per minute.
Explanation:
Let x represent his speed in still air.
Let y represent the speed of the wind.
It takes Jack Frost 5 minutes to fly 35 miles with the wind. This means that his total speed would be x + y
Distance = speed × time
It means that
35 = 5(x + y)
35 = 5x + 5y - - - - - - - - - - -1
It takes him 7 minutes to go 35 miles against the wind. This means that his total speed would be x - y
It means that
35 = 7(x - y)
35 = 7x - 7y - - - - - - - - - - -2
Multiplying equation 1 by 7 and equation 2 by 5, it becomes
245 = 35x + 35y
175 = 35x - 35y
Adding both equations, it becomes
420 = 70x
x = 420/70 = 6
Substituting x = 6 into equation 1, it becomes
35 = 5 × 6 + 5y
35 = 30 + 5y
5y = 35 - 30 = 5
y = 5/5 = 1