Respuesta :

BrainIess
Equation 1 ==> y - x = -13
Equation 2 ==> -4x + 3y = -51
3(y - x) = 3(-13)
Equation 3 ==> 3y - 3x = -39

Equation 2 - 3
= (3y - 3y) + ( -4x - (-3x) ) = -51 - (-39)
-x = -12
x = 12

Substitude x into equation 1
y - 12 = -13
y = -1