Given data:
The speed of the plane when it flies from Houston to Denver is a=(x+60) mph.
The speed of the plane when it flies from denver to Houston is b=(x-60) mph.
The time taken by the plane when it flies from Houston to Denver is t=2.4 h.
The time taken by the plane when it flies from Denver to Houston is t'=2.76 h.
Assume the distance bewteen Houston to Denver is y.
The distance when the plane flies from Houston to Denver is,
y=(x+60)2.4
y=2.4x+144.......(I)
The distance when the planne flies from Denver to Houston is,
y=2.76(x-60)
y=2.76x-165.6......(II).
Equate both the equations.
2.4x+144=2.76x-165.6
309.6=2.76x-2.4x
x=860 mph
The distnace between Houston to Denver is,
y=(860+60)2.4
=2,208 miles.
Thus, the distance between Houston and Denver is 2,208 miles.