A 75ft diagnol brace on a bridge connects a support of the center of the bridge The horizontal distance that it spans is 15ft longer than the hieght that reaches on the side of the bridge.Find the horizontal and vertical distance spanned by this brace

If I am picturing this correctly, a right triangle is formed, with the diagonal of 75' being the hypotenuse.

x = one leg (vertical height)
x + 15 = other leg (horizontal distance)

Use the Pythagorean theorem,
c^2 = a^2 + b^2
75^2 = x^2 + (x + 15)^2

Solve for x