# How do you solve the system 4x+8y= -20 and 7x-3y= -1?

Apr 22, 2018

Substitution

#### Explanation:

$4 x + 8 y = - 20$ --- 1
$7 x - 3 y$ = -1--- 2
Multiply equation 1 by 7 and equation 2 by 4.
$28 x + 56 y = - 140$
$28 x - 12 y$ = -4
Make $28 x$ the subject,
$28 x = - 140 - 56 y$
$28 x = - 4 + 12 y$
Equate the equations,
$- 140 - 56 y = - 4 + 12 y$
$- 136 = 68 y$
$y = - 2$