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