# M:C:MC:19

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If is a solution to the system of equations above, what is the value of

### Select an Answer

-51

3

9

144

### View Correct Answer

Choice C is correct. The second equation gives *y* in terms of *x*, so a student can use this to rewrite the first equation in terms of *x*. Substituting -4*x* for *y* in the equation gives This can be simplified to or Since the question asks for the value of not *x*, dividing both sides of by 17 gives the answer:

Choice A is not the correct answer. This answer may result from neglecting to square the coefficient –4 in which would give Then the first equation would become which would give –51 as the value of

Choice B is not the correct answer. This answer may result from finding the value for *x*, not the value of

Choice D is not the correct answer. This answer may result from finding the value of not

Students must manipulate one equation for use in another, in order to solve for a given value, making use of familiar algebraic arrangements where appropriate.