How do you solve the following system?: 5x +5y =27, 9x -5y = 0

1 Answer
r3cebarnett
Nov 12, 2015

By substitution.

Explanation:

We have two equations, 5x+5y=27 and 9x-5y=0. In order to use substitution, we need to solve for one variable. The easiest one to solve for would be 9x-5y=0

9x-5y=0
9x=5y

Now looking at the equation we need to substitute in for, it would be easier for us to plug something in with a denominator of 5 so they would cancel out and we can do a little less math. So we shall solve for y in this equation.

y = 9/5x

Now we plug this y into the other equation.

5x+5(9/5x)=27 and simplifying this would give us
5x+9x=27 now we need to combine like terms
14x=27 and finally
x=27/14

Now we plug this into the other equation.

9(27/14) - 5y = 0

243/14 - 5y = 0

243/14 = 5y

243/70 = y

My calculator isn't working right now so I can't quite give you decimal values but those fractions should be correct.

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