Question

I don’t understand the concept of this problem

Answer 1

This uses the method of elimination/addition.

Explanation:

1 (9x + 7y = 15)

-7 (5x + y = -9) <— let’s eliminate y for both equations

9x + 7y = 15

+ -35x - 7y = 63 <— add both of the equations

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- 26x + 0y = 6

(Please let me know if the answer is correct or not)