you can solve the equestion by many rules , but in my point of view the easiest rule is subtraction/addition and subtition method .
Ans X=11.5
Y = -39
8x+2y=14 eqn.......1
82+2y=4 eqn .......2
2y= -78 (4-82)
y = - 39
putting value of y in eqn ..1
we get,
8x+ 2×(-39) =14
8x= 14+78
8x=92
x = 92÷8
x=11.5
it's a subtition method..