Throwing a ball, shooting a cannon, diving from a platform and hitting a golf ball are all examples of situations that can be modeled by quadratic functions. ... In many of these situations you will want to know the highest or lowest point of the parabola, which is known as the vertex.
13 divided by 11.3 is 1.150442477876106. So 15 by 1.150442477876106 and you get 13.03846162772485. Just round it to the nearest tenth and you get 13.0.