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About Lynn Houston
Expertise
I can answer questions in basic algebra and any grade school math.

Experience
Love math, currently helping my nephew get through Intermediate Algebra.

Education/Credentials
I majored in Math Ed in college (but decided not to teach), so have over 40 credits of math.

 
   

You are here:  Experts > Science > Math for Kids > Basic Math > Subitution Math Problem

Basic Math - Subitution Math Problem


Expert: Lynn Houston - 11/6/2009

Question
What are the steps to this substitution
y=9x-28
8x-3y=27

Answer
You take the value of y, which is 9x-28 and you fill that into the second equation for y.

8x - 3(9x-28) = 27  Do the multiplication
8x - 27x + 84 = 27  add like terms
-19x + 84 = 27      subtract 84 from both sides of the equation
-19x = -57          divide both sides by -19
x = 3   now you do the same thing with the value of x, fill it into the first eq

y = 9(3) - 28
y = 27 - 28
y = -1

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