Answer:
13) (-2,-3) 14) (7,-4) 15) (-8,7)
Explanation:
13) y=8x+13
-4x-5y=23
use substitution
-4x-5(8x+13)=23
distribute -5 in the parenthesis
-4x-40x-65=23
-44x-65=23
add 65 on both sides
-44x=88
divide both sides by -44
x=-2
for y...
y=8(-2)+13
y=-16+13
y=-3
answer is (-2,-3)
14) -3x-y=-17
y=-4x+24
use substitution
-3x-1(-4x+24)=-17
distribute the -2 in the parenthesis
-3x+4x-24=-17
x-24=-17
add 24 on both sides
x=7
for y...
y=-4(7)+24
y=-28+24
y=-4
answer is (7,-4)
15)5x+4y=-12
y=-2x-9
use substitution
5x+4(-2x-9)=-12
distribute 4 in the parenthesis
5x-8x-36=-12
-3x-36=-12
add 36 on both sides
-3x=24
divide both sides by -3
x=-8
for y...
y=-2(-8)-9
y=16-9
y=7
answer is (-8,7)