1) In order to use the elimination method to solve systems of equations, you must first multiply one or both of the equations so that the coefficients of a pair of terms with matching variables share the same number, but have opposite signs.
In this case, the y terms must fit that requirement. The y term in the first equation is 2y and the one in the second equation is -y. They already have opposite signs, one positive and other negative, so we just need -y to be -2y. So, in order to do that, multiply by 2.
2) After multiplying the whole second equation by 2, you will get . Now, add the the two equations together, eliminate the y terms, and isolate x to find its value.
3) Then, substitute that x value back into one of the equations to receive the y-value.
To better explain these steps, I attached pictures below.