Please help me. I can't figure out how to solve this problem.

The cable of a suspension bridge hangs in the form of a parabola when the load is evenly distributed horizontally. The distance between the two towers is 150m, the points of support of the cable on the towers are 22m above the roadway, and the lowest point on the cable is 7m above the roadway. find the vertical distance to the cable from a point in te roadway 15m from the foot of the tower.