3x-y=11 and 5y-7x=1 Substitution

Question

Algebra 1 Substitution.

Answer 1

Hello Gretchen,

3x - y = 11

5y - 7x = 1

How about we substitute for "y" and solve for "x?" Therefore:

y = 3x - 11

Next, we substitute:

5(3x - 11) - 7x = 1 <----Using the second equation we simply substituted 3x - 11 for "y"

15x - 55 - 7x = 1 <----Used distributive law on left side and arrived at this

8x - 55 = 1 <-----Combined like terms

8x = 56 <------Added 55 to both sides of the equation

x = 7 <------The value of x

Now, let's solve for "y," okay?

y = 3x - 11 <------This is what "y" originally solved for

y = 3*7 - 11 <------Substituted 7 for "x."

y = 21 - 11 <------Multiplied 3 in equation by value of "x" which is 7

y = 10 <------Value of y.

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