There are two ways to do this but the way I prefer is to make one of the equations in terms of one variable and then 'plug this in' to the second equation. I will demonstrate
Look at equation 1,
this can quite easily be manipulated to show 
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Then because there is a y in the second equation (and both equations are simultaneous) we can 'plug in' our new equation where y is in the second one
which can then be solved for x since there is only one variable 
and then with our x solution we can work out our y solution by using the equation we manipulated 
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So the solution to these equations is x=-2 when y=6
Look at equation 1,
Then because there is a y in the second equation (and both equations are simultaneous) we can 'plug in' our new equation where y is in the second one
So the solution to these equations is x=-2 when y=6