I need help with these questions.. Can someone help?

Question

anonymous · Answer

[6.02] 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

lol

jim_thompson5910 · Answer

what do you get when you solve

−x + 2y = 9

for x

anonymous · Answer

I got -9 but idk what i did was right

jim_thompson5910 · Answer

to solve −x + 2y = 9 for x, you just need to isolate it

−x + 2y = 9

−x = 9 - 2y

x = -9 + 2y ...remember, we want x NOT -x (so change the sign of each term)

jim_thompson5910 · Answer

so after solving −x + 2y = 9 for x, we get

x = -9 + 2y

jim_thompson5910 · Answer

this will allow you to replace the 'x' in the second equation with -9 + 2y (ie you are substituting one thing for another so you can solve)

anonymous · Answer

I get it thank you very much!!! :)

jim_thompson5910 · Answer

you're welcome