# How do you solve by substitution a = 3b - 4 and a + b =16?

Apr 2, 2018

$b = 5$
$a = 11$

#### Explanation:

$a = 3 b - 4$ ----(1)
$a + b = 16$----(2)

From (2),
$a = 16 - b$ ----(3)

Sub (3) into (1)
$16 - b = 3 b - 4$
$20 = 4 b$
$b = 5$
$a = 11$

Apr 2, 2018

$a = 11$ and $b = 5$

#### Explanation:

We know a in terms of b with the help of equation 1 $a = 3 b - 4$

So put that that in equation 2,
$3 b - 4 + b = 16$
$4 b = 20$
$b = 5$
$a + 5 = 16$
$a = 11$
So $a = 11$ and $b = 5$