yet the answer i should get is . what step am i doing wrong on this algebra problem?

when you have polynomials multiplication, say (x+y) (a+b+c), you can always just multiply x(a+b+c) + y(a+b+c), namely each term by all others and sum them up, like above.

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: