# How do you solve this set of linear equations: 9x - 2y = 11; 5x - 2y = 15?

##### 1 Answer
Oct 9, 2016

$x = - 1 \mathmr{and} y = - 10$

#### Explanation:

$9 x - 2 y = 11 \text{ and } 5 x - 2 y = 15$

Notice that there is -2y" in each of the equations.

Make $2 y \text{ }$the subject in each case.

$2 y = 9 x - 11 \text{ and } 2 y = 5 x - 15$

$\textcolor{w h i t e}{\times \times \times \times x} 2 y = 2 y$

$\textcolor{w h i t e}{\times \times x} 9 x - 11 = 5 x - 15$

$\textcolor{w h i t e}{\times \times x} 9 x - 5 x = - 15 + 11$

$\textcolor{w h i t e}{\times \times x . \times x} 4 x = - 4$

$\textcolor{w h i t e}{\times \times \times \times x} x = - 1$

$2 y = 9 x - 11 \text{ } \leftarrow$ substitute $- 1 \text{ for } x$

$2 y = 9 \left(- 1\right) - 11$

$2 y = - 9 - 11$

$y = - \frac{20}{2}$

$y = - 10$