GreenlightTestPrep wrote:
If 6x - 7y = 11 and -5y = 13 + 5x, what is the sum of x and y?
(A) -5.2
(B) -2.6
(C) -1.3
(D) 1.3
(E) 2.6
Given: 6x - 7y = 11 and -5y = 13 + 5xFirst things first, let's rearrange the terms in the second equation so that they match up with the terms in the first equation.
Take: -5y = 13 + 5x
Add 5y to both sides of the equation: 0 = 13 + 5x + 5y
Subtract 13 from both sides of the equation: -13 = 5x + 5y
Rewrite as: 5x + 5y = -13
We get:
6x - 7y = 11
5x + 5y = -13Wait a second!
Notice that the question does NOT ask us to find the individual values of x and y.
We just need to find the value of x + y
We can take
5x + 5y = -13 and factor the left side to get
5(x + y) = -13So, if we divide both sides of the equation by 5, we get:
x + y = -2.6Bingo!!!
Answer: B
Cheers,
Brent