SOLUTION: I need help to solve this system using substitution {{{y= (-4/5) x-10}}} {{{2x +y =20}}}

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Question 129682: I need help to solve this system using substitution
y=+%28-4%2F5%29+x-10
2x+%2By+=20
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
2X+Y=20 OR Y=20-2X
20-2X=(-4/5)X-10
20-2X=-4X/5-10
-2X+4X/5=-10-20
(5*-2X+4X)/5=-30
-10X+4X=-150
-6X=-150
X=-150/-6
X=-25 ANSWER.
Y=20-2*-25
Y=20-50
Y=-30 ANSWER.
PROOF:
-30=(-4/5)*-25-10
-30=100/5-10
-30=-20-10
-30=-30