# How do you solve  5x – 6y = 21 and x - 2y = 5 using substitution?

Mar 5, 2016

Solution is $x = 3$ and $y = - 1$

#### Explanation:

To solve 5x–6y=21 and x−2y=5 using substitution, we first get value of $x$ from second equation and put it in first equation.

From second equation x−2y=5, we get $x = 5 + 2 y$ ... (A)

Hence second equation becomes

5(5+2y)–6y=21 i.e. $25 + 10 y - 6 y = 21$ or

$4 y = 21 - 25 = - 4$ and hence $y = - \frac{4}{4} = - 1$.

Now putting this in (A), we get $x = 5 + 2 \times \left(- 1\right)$ or

$x = 5 - 2 = 3$

Hence solution is $x = 3$ and $y = - 1$