Answer:
x = -3 and y = -4
x + y = -3-4 = -7
Explanation:
-4x + 9y = -11 ------------------------------------------------------------------------(1)
-3x + 7y = -9--------------------------------------------------------------------------(2)
multiply through equation (1) by 3 and multiply through equation(2) by 4
-12x + 27y = -33 -----------------------------------------------------------------------(3)
-12x + 28y = -36 ----------------------------------------------------------------------(4)
subtract equation (1) from equation (2)
y = -3
substitute y = -3 into equation (2)
-3x + 7(-3) = -9
-3x -21 = -9
add 21 to both-side of the equation
-3x -21 + 21 = -9 + 21
-3x = 12
divide both-side of the equation by -3
-3x/-3 = 12/-3
x = -4
x = -3 and y = -4