8 x 4 = (y x 7) - (y x 3)

What is y?

8x4=32

32 = (yx7) - (yx3)

(yx7) = 7y

(yx3) = 3y

32=7y-3y

7y and 3y are like terms so you subtract them

=4y

32=4y

then divided 4y by 4 (to get y on its own) this cancels out if you : 4y on one side of the equation you have to divide on the other side to make it balanced 32:4=8

y=8