For the following system, if you isolated x in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

−x + 2y = 9
4x + 5y = 9

A.–9 + 2y
B.–9 − 2y
C.9 – 2y
D.9 + 2y

Question

For the following system, if you isolated x in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

−x + 2y = 9
4x + 5y = 9  

A.–9 + 2y
B.–9 − 2y
C.9 – 2y
D.9 + 2y

anonymous · Answer

$$x=2y-9 --> -x+2y=9$$
sub in this equation in 4x+5y=9
$$4(2y-9)+5y=9$$
$$8y-36+5y=9$$
$$13y=9+36$$
$$13y=45$$
$$y=\frac{ 45 }{ 13 }$$

the answer is A

anonymous · Answer

(: