Question 324138
There is no picture, so I will try to extrapolate.

Center it at the origin. The parabola representing the bridge arch passes through (50,0) and (-50,0) and has its vertex at (0,75).

We can use the equation {{{y=a(x-h)^2+k}}} to model the parabola.

Plug in the given points and solve for a.

{{{0=a(50-0)^2+75}}}

{{{0=a*2500+75}}}

{{{a=-75/2500=-3/100}}}

Therefore, the parabola equation is 

{{{y=-3/100*x^2+75}}}

To find how high it is at a point, simply plug in the corresponding x value.

i.e. How high is the arch at x=25?

{{{-3/100*(25)^2+75=56.25}}} m