PLEASE help with a few Algebra 2 question?

12.
- 5x^2 + 5 = - 2x
5x^2 - 2x - 5 = 0
x = ( 2 ± √104 ) / 10 = ( 1 ± √26 ) / 5
Ans: D

13.
x = 7y substitute into next 2 equations, we get :
8y + z = 80 ..... (1)
13y + z = 105 ..... (2)
(2) - (1) :
5y = 25
y = 5
Ans: E

14.
3√45 - 5√5 = 9√5 - 5√5 = 4√5

( 3√45 - 5√5 ) / ( 3√5 - 5√3 )
= 4√5 / ( 3√5 - 5√3 )
= 4√5( 3√5 + 5√3 ) / [ ( 3√5 - 5√3 )( 3√5 + 5√3 ) ]
= ( 60 + 20√15 ) / ( 45 - 75 )
= ( 60 + 20√15 ) / ( - 30 )
= - 2 - (2/3)√15
Ans: B