Solve by Substitution x+7y=5 , 4x+8y=-20

Problem

{[x+7*y=5],[4*x+8*y=−20])

Solution

1. Isolate the variable x in the first equation by subtracting 7*y from both sides.

x=5−7*y

2. Substitute the expression for x into the second equation.

4*(5−7*y)+8*y=−20

3. Distribute the 4 into the parentheses.

20−28*y+8*y=−20

4. Combine the like terms involving y

20−20*y=−20

5. Solve for y by subtracting 20 from both sides and then dividing by −20

−20*y=−40

y=2

6. Substitute the value of y back into the isolated equation for x

x=5−7*(2)

x=5−14

x=−9

Final Answer

(x,y)=(−9,2)

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