Algebra practice question

Answer: A. 7

Add the two equations: the y terms cancel, leaving 2x = 14, so x = 7. (Then y = 3.) Check: 7 + 3 = 10 and 7 − 3 = 4.

Why the other answers are wrong

B. 3

3 is the value of y, not x. Adding the equations eliminates y and gives x = 7 first.

C. 14

14 is 2x, the result of adding the equations. Divide by 2 to get x.

D. 6

6 is 10 − 4, subtracting the right-hand sides for no reason. Subtracting the equations eliminates x, not y: 2y = 6 gives y = 3.

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