Abird leaves its nest and travels 20 miles per hour downwind for x hours. on the return trip, the bird travels 4 miles per hour slower and has 6 miles left after x hours.

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: