You have the following system of equations:
6x + 3y = 12
4x - y = 14
in order to solve the previous system, use the subtraction method. Proceed as follow:
Multiply the second equation by 3 and sum the result to the first equation, in this way you aliminate x variable and can solve for y:
(4x - y = 14)(3)
12x - 3y = 42
6x + 3y =