Respuesta :

Use elimination to create a one variable equation.

 x-3y=15 -> 2x-6y=30

   2x-6y=30

+(-2x-4y=10)

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-10y=40

Then solve (for y in this case).

y=-4

Now we can use the value for y to solve for x.

x-3y=15 -> x-3(-4)=15 -> x=3