Answer:
Truck time - car time = 2 hrs so,
(350/s) - [350/(s+20)] = 2
LCD we can get
[350(s+20) - 350s]/s(s+20) = 2
then transpose the denominator
350(s+20) - 350s = 2s(s+20)
simplifying we can get
350s + 7000 - 350s = 2s^2 + 40s
then simplify more to become quadratic equation
2s^2 + 40s - 7000 = 0
to make it simplest divide the equation by 2
s^2 + 20s - 3500 = 0
by factoring we can get
s= 50
s= -70 (impossible because of the sign)
