Alaboratory designed a radio telescope with a diameter of 380 feet and a maximum depth of 42 feet. the graph depicts a cross section of this telescope. find the equation of this parabola.

We don't get to see the graph, so will assume the simplest equation with vertex at origin.
The equation is
y=ax^2
with x=380/2=190', y=42'
so 
42=a(190^2) => a=42/190^2=21/18050

the equation is therefore
y=21x^2/18050 
and kept in exact form above for accuracy required for a telescope.

If the graph shows the vertex elsewhere at (h,k), the equation is then 
y=21(x-h)^2/18050+k

60 ÷ -20 x makes x = -3