You can put this solution on YOUR website!
-7x + 8y + 3y = 10
28x/4 - 12y = 7
-7x + 11y = 10
7x - 12 y = 7
then all you need to do is adding the equations
(-7x + 11y) + (7x - 12y) = 10 + 7
=) -7x + 11y + 7x - 12y = 17
now you need to find the sum of x's and y's
=) 7x-7x + 11y-12y = 17
=) 0 + -y = 17
so you got rid of x. now you need to multiply both sides with negative one.
=) y = -17
so we found the y. now all you need to do is to substitute it with one of the equations you gave. i chose "28x/4 - 12y = 7"
7x - 12(-17) = 7
7x + 204 = 7
now we need to have x in one side and the number in the other side
7x = 7-204
7x = -197
you need to divide both sides wth "7"
x = -28,142857
if you want to show the x as a fraction it is -2
so that is it!