Question 1171136
A big mistake here, I assumed the towers were 400 ft from the midpoint, not so
they are 200 ft from the center
here is is again
let the midpoint be 0, 30 on a graph, then find the equation for 200, 150 
x=200, y=150
200^2a + 30 = 150
40000a = 150-30
a = 120/40000
a = .003
The equation
y = .003x^2 + 30
graphically
{{{ graph( 300, 200, -250, 250, -20, 200, .003x^2+30, 98) }}}
:
"how high is the cable 50 feet away(horizontally) from either tower?"
200-50 = 150, find y when x = 150
y = .003(150^2) + 30
7 = 67.5 + 30
y = 97.5 is the height of the cable at this point (Green line)