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Algebra / Systems of two linear equations in two variables Difficulty: Easy

4 x = 20

- 3 x + y = -7

The solution to the given system of equations is x,y. What is the value of x + y ?

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Explanation

Choice C is correct. It's given that 4 x = 20 and - 3 x + y = -7 is a system of equations with a solution x,y. Adding the second equation in the given system to the first equation yields 4x+(-3x+y)=20+-7, which is equivalent to x+y=13. Thus, the value of x+y is 13

Choice A is incorrect. This represents the value of -2x+y-1.

Choice B is incorrect. This represents the value of -x+y.

Choice D is incorrect. This represents the value of 2x+y+1.