Given triangle abc, (1,8), (-5, 13) and (7, 13) what type of triangle do these points make

Check the picture below.

so the vertex at the bottom is exactly half-way of the opposite side, and equidistant from the other two vertices, meaning the two slanted sides are twins, and thus this is an isosceles triangle.

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: