Number 10.
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Number 12.
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Number 14.
If you show that the example is showing a false statement then you are disproving the example/problem.
1. GCF is 7 so answer is 7(5+6)
2. GCF is 5 so answer is 5(3+8)
Explanation:
Basically, you can do it in many ways. But just, in my opinion, exactly linear algebra was made for such cases.
the optimal way is to do it with Cramer's rule.
First, find the determinant and then find the determinant x, y, v, u.
Afterward, simply divide the determinant of variables by the usual determinant.
eg.
and etc.
I think that is the best way to solve it without a hustle of myriad of calculations reducing it to row echelon form and solving with Gaussian elimination.