# How do you solve for a in ab + c = d?

Jul 7, 2016

$a = \frac{d - c}{b}$

#### Explanation:

Remember we can do pretty much anything we like to an equation as long as we do the same to both sides.

Subtract $c$ from both sides:

$a b + c \textcolor{red}{- c} = d \textcolor{red}{- c}$

$\therefore a b = d - c$

Divide both sides by $b$

$\frac{a b}{\textcolor{red}{b}} = \frac{d - c}{\textcolor{red}{b}}$

$\therefore a = \frac{d - c}{b}$