Question 890364
d = r*t
t = d/r
39/(b+5) + 39/(b-5) = 12
13/(b+5) + 13/(b-5) = 4
15(b+5) + 13(b-5) = 4(b^2-5)
26b = 4b^2 - 20
2b^2 - 13b - 10 = 0
Solve for b