# How do you solve the system 2x-3y=21 and y=3-x using substitution?

Mar 3, 2017

$x = 6$ & $y = - 3$
Solution : $\left(6 , - 3\right)$

#### Explanation:

$2 x - 3 y = 21$ ------------(1)

$y = 3 - x$-----------------(2)

Substituting eq 2 in eq 1

$2 x - 3 \left(3 - x\right) = 21$

$2 x - 9 + 3 x = 21$

$5 x - 9 = 21$

$5 x = 30$

$x = 6$

Put $x = 6$ in eq 2 we get,

$y = 3 - 6$

$y = - 3$

Solution : $\left(6 , - 3\right)$