Question 1054732
12/r + 12/(r+10) = 1
Multiply thru by r(r+10)
12(r+10) + 12r = r(r+10)
12r + 120 + 12r = r^2 + 10r
r^2 - 14r - 120 = 0
(r + 6)(r-20) = 0
r = {{{highlight(20mph)}}}  and r+10 =  {{{highlight(30mph)}}}