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11 votes
Below, explain why we are allowed the

"substitute in" x - 3 for y in the top equation.
Why is this useful for finding our first solution?
x + y = 11
y = x - 3

1 Answer

9 votes

Answer:

because in the bottom eqution it shows us x-3=y therefor we could re-write the top equation as x+x-3=11

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