# How do you solve the system by substitution x + y = 12 and y = 2x?

Oct 1, 2016

Solution is $x = 4$ and $y = 8$

#### Explanation:

We have two equations $x + y = 12$ and $y = 2 x$

Let us substitute value of $y$ from second equation in the first equation.

As $y = 2 x$, substituting this in first we get

$x + 2 x = 12$

or $3 x = 12$

or $x = \frac{12}{3} = 4$

and hence $y = 2 x = 2 \times 4 = 8$, therefore

Solution is $x = 4$ and $y = 8$