Solve x + 3y = 9
3x – 3y = –13

a. (–1, ten thirds)
b. (1, negative ten thirds)
c. (–1, 3 over 10)
d. (1, negative 3 over 10)

Question

Solve x + 3y = 9
3x – 3y = –13

a. (–1, ten thirds)
b. (1, negative ten thirds)
c. (–1, 3 over 10)
d. (1, negative 3 over 10)

callisto · Answer

x + 3y = 9             -(1)
3x – 3y = –13        -(2)
(1)+(2)
(x + 3y) + (3x – 3y) = 9 + (-13)  <- Can you solve it?

anonymous · Answer

@Callisto

-3(x + 3y = 9) 
3x – 3y = –13

-3x - 9y = -27
  3x – 3y = –13
      -12y = -58
           y = 58
                ---
                 12

callisto · Answer

It's good that you did it using your way~
Though, there are some problems..

-3x - 9y = -27  <- correct
  3x – 3y = –13   <-correct
      -12y = -58   <- something wrong with the right side, can you check what -27-13 is?
           y = 58      <- incorrect
                ---
                 12

anonymous · Answer

-12y = 14

callisto · Answer

No...
what is -27-13??

anonymous · Answer

-40

callisto · Answer

Yes.
So, for the right side, you get -40, and for the left, you got -12y. Can you solve it?
(-12y=-40)

anonymous · Answer

-40         -20           -10
---   =   ------  =  -----
-12         - 6               -3

callisto · Answer

-10/-3 can be further simplified by cancelling the common factor -1. What is the final answer you got for y?

anonymous · Answer

y = 10
    - ___
        3

instead of replacing Y in the other equations and such, since there's only one answer choice with this number, can't we determine that it is the correct answer?

callisto · Answer

No negative sign indeed! negative/ negative = positive

anonymous · Answer

ohhh, okay, so the answer is A. ?