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

In the xy-plane, the graph of y equals, x plus 3 intersects the graph of y equals, 2 x minus 6 at the point with coordinates a, comma b. What is the value of a ?

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Explanation

Choice C is correct. Since the graph of y equals, x plus 3 intersects the graph of y equals, 2 x minus 6 at the point with coordinates a, comma b, the ordered pair a, comma b is the solution to the system of linear equations consisting of y equals, x plus 3 and y equals, 2 x minus 6, and the value of a is the value of x in the solution of this system. Since both x plus 3 and 2 x minus 6 are equal to y, it follows that x plus 3, equals, 2 x minus 6. Subtracting x from and adding 6 to both sides of the equation yields 9 equals x. Therefore, the value of a is 9.

Choices A and B are incorrect and may result from a calculation or conceptual error in solving the system of equations consisting of y equals, x plus 3 and y equals, 2 x minus 6. Choice D is incorrect. This is the value of b, not a.