We are working with two numbers. Let's call them m and n.
When added together, they will equal 45. When they are subtracted, they will equal 13. The answer that matches this is A.
We might as well solve it. You can figure this out using elimination, since we have a really nice setup for that method.
m+n=45
+ m-n=13
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This simplifies to 2m=58, making m=29. We then plug this into the first equation to find n.
29-n=13
Simplified gets us n=16. We see that if we plug this into both equations, they are true.
:)
