Two Angles are Supplementary when they add up to 180 degrees. Notice that together they make a straight angle. But the angles don't have to be together.
Y = 5 - 3x....so sub in 5 - 3x for y in the other equation
5x - 4y = -3
5x - 4(5 - 3x) = -3.....distribute the -4 thru the parenthesis
5x - 20 + 12x = -3...add 20 to both sides
5x + 12x = -3 + 20...combine like terms
17x = 17...divide both sides by 17
x = 17/17
x = 1
now sub 1 in for x into either of the original equations to find y
y = 5 - 3x
y = 5 - 3(1)
y = 5 - 3
y = 2
check...
5x - 4y = -3
5(1) - 4(2) = -3
5 - 8 = -3
-3 = -3 (correct)
so ur solution is (1,2)
