Consider this system of linear equations:
y − x = -13
-4x + 3y = -51
the solution of the system of equations is

Y - x = -13y = x - 13
now sub x - 13 in for y into the other equation

-4x + 3(x - 13) = -51
-4x + 3x - 39 = -51
-4x + 3x = -51 + 39
-x = - 12
x = 12

y = x - 13
y = 12 - 13
y = -1

ur solution is : (12,-1)