Hello from MrBillDoesMath!
Answer:
x = -3, y = 4
Discussion:
x + y = 1 =>
y = 1 -x
Substitute this y value into the second equation:
5x + 3y = -3 =>
5x + 3(1-x) = -3 => 3(1-x) = 3 -3x
5x + 3 - 3x = -3 => 5x -3x = 2x
2x + 3 = -3 => subtract 3 from both sides
2x = -3 -3 = -6 => divide both dies by 2
x = -6/2 = -3
As x+y = 1, (-3) + y = 1 => y = 1 + 3 = 4
Thank you,
MrB