Amodel of a building is made using a scale of 1 inch = 20 feet. what is the height of the actual building if the height of the model is 10.5 inches.

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: