Just solve vertically.
So first add 3x and -3x, and they cancel out. So the terms with the x variables have been eliminated.
Then, add -y and 3y to get 2y on the left side of the equation.
Lastly, add -1 and 26 to get 26 on the other side (right side) of the equation.
So, in all, you have 2y=26 as the resulting equation, after you add them.
Thus, option C is the correct answer.
