What are the two ratios that are equivelent to 15: 20

Which of the following expressions are equivalent ?

Monica build a remote control toy airplane for science project to test the plane she launched it from the top of a building the plane travel a horizontal distance of 50 feet before landing on the ground a quadratic function which models the height of the plane in feet relative to the ground at a horizontal distance of x feet from the building is shown

Ineed with number 6 , explain how to get 1978