If you have multiple equations with multiple variables, you can either do clever substitutions, or turn it into a matrix on which you can perform linear combinations or multiplications (Gauss elimination)
1 1 1 1 2 1 -1 8 1 -1 1 -5
(note how the above 3 rows represent the 3 equations, just got rid of the variables, plus sign and equals sign)
subtract row1 from row3, that eliminates x and z from row 3.
So we need to plug in our values so now y=4(3)-9 so 4*3 is 12 now we have y=12-9 Subtract 12 and nine to get 3 so y equals 3. The answer is (3, 3). Hope this helped please look at others answers and check other resources as well
