Quadratic Equation

1)
Let the original speed of the car be x km/h
If the speed of the car is increased by 15km/h, the journey takes 4/5 of an hour less.
The old time-The new time=4/5 hour
(240/x)-240/(x+15)=4/5
240(x+15)-240x=(4/5)x(x+15)
3600=(4/5)(x^2+15x)
18000=4x^2+60x
4x^2+60x-18000=0
x=60 or x=-75 (rejected)

2)
Let the original fraction be n/(n+4)
If both the numerator and the denominator are increased by 3, then the fraction will be increased by 1/9. find the original fraction.
(n+3)/(n+4+3)-n/(n+4)=1/9
(n+3)/(n+7)-n/(n+4)=1/9
(n+3)(n+4)-n(n+7)=(1/9)(n+4)(n+7)
n^2+7n+12-n^2-7n=(1/9)(n^2+11n+28)
12=(1/9)(n^2+11n+28)
n^2+11n+28=108
n^2+11n-80=0
n=5 or n=-16 (rejected)
The original fraction is 5/9