Question 324137
 8x + 7y = 12
-7x - 4y = -2

1)First, you have to make one of the numbers the same in order to eliminate it.
  So, first, multiply the whole first equation by 7 and the whole second
  equation by 8. The new equation should look like this:
   56x + 49y = 84
  -56x - 32y = -16

2)Next, subtract the numbers. (Elimination)
   49y = 84
  -32y = -16

  17y = 68
  y = 4

3)Now that you have the answer to y, you have to find x. So now, we make the
  numbers for y the same. So, multiply the first equation by 4 and the second
  equation by 7.
   32x + 28y = 48
  -49x - 28y = -14

4)Now, subtract.
   32x = 48
  -49x = -14

  -17x = 34
  x = -2