Answer:
4. 
5. 
6.
or 3.5
Step-by-step explanation:

Multiply those 2 values whose diagonal has both terms and divide by the term whose diagonal has the variable.

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X= 12 and y=12
Explanation: To get the variables alone, you multiply each by 0. That would leave you with x-y=12. So the x is 12 and the y is 12. Hope this helped!