Answer:
see below
Step-by-step explanation:
You can add any multiple of one equation to the other without changing the solution to the system.
In the first answer choice the first equation is added to the second, and the first equation is left alone.
In the third answer choice, the first equation is subtracted from the second, and the second equation is left alone.
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The other answer choices have strange combinations of sums and differences that result in systems of equations with different answers.
