# How do you use the substitution method to solve 3x-15y=-12 and 3x+24y=-12?

##### 1 Answer
Jun 26, 2015

Derive an expression for $3 x$ from the first equation, then substitute that in the second equation and solve to find $y = 0$ and $x = - 4$

#### Explanation:

First add $15 y$ to both sides of the first equation to get:

[1] $3 x = 15 y - 12$

Then substitute $15 y - 12$ for $3 x$ in the second equation to get:

$\left(15 y - 12\right) + 24 y = - 12$

Add $12$ to both sides and combine the remaining terms to get:

$39 y = 0$

Divide both sides by $39$ to get $y = 0$

Then substitute $y = 0$ in [1] to get:

$3 x = - 12$

Divide both sides by $3$ to get $x = - 4$