# How do you solve the following linear system:  2x + 4y = 7 , x + y = 3 ?

Jan 23, 2016

From the second expression you can derive that $y = 3 - x$ (by subtracting $x$ from both sides.

#### Explanation:

Now you can substitute (=replace) every $y$ in the first expression by this value:
$\to 2 x + 4 \cdot \left(3 - x\right) = 7$ work away the brackets:
$\to 2 x + 12 - 4 x = 7$ put together and subtract 12 on both sides:
$\to 2 x - 4 x = 7 - 12 \to - 2 x = - 5$

$\to x = 2 \frac{1}{2} \to y = 3 - 2 \frac{1}{2} = \frac{1}{2}$

Just to make sure, you will want to put the answers back into the question.