Answer:
x = -4,
y = -1
Explanation:
{-3x - 8y = 20,
{-5x + y = 19;
Make x or y the subject from either the 1st or the 2nd equation (I chose to make x the subject from the 2nd equation, because after division, the numbers can be written as a finite decimal fraction):
-5x = 19 - y / : (-5)
x = -3,8 + 0,2y
Replace x in the 1st equation with its value from the 2nd one (the underlined expression):
-3(-3,8 + 0,2y) - 8y = 20
Multiply every term inside the bracket by the term on the outside:
11,4 - 0,6y - 8y = 20
Collect like terms and add them together:
-8,6y = 20 - 11,4
-8,6y = 8,6 / : (-8,6)
y = -1
y = -1x = -3,8 + 0,2 × (-1) = -4