# Having trouble with formulas (Equations & Transpositions)

#### jayinwww

Solve for A

b = 1/2h (A + C)

My first step is to minus C on both sides so I got

b - C = 1/2h A then i flip the 1/2 to 2/1 so it's b - C = 2h A

My second step is to divide both sides by 2h..

b-c/2h = A

But in my text book it says the answer is

A = 2b/h - C

I don't get it, where did i go wrong?

#### skeeter

Math Team
Solve for A

b = 1/2h (A + C)
your very first step is incorrect. you cannot subtract $c$ from inside the parentheses.

$b = \dfrac{1}{2}h(a+c)$

multiply both sides by 2 ...

$2b = h(a+c)$

divide both sides by $h$ ...

$\dfrac{2b}{h}=a+c$

subtract $c$ from both sides ...

$\dfrac{2b}{h}-c=a$

2 people

#### deesuwalka

$b=\dfrac{1}{2}h(a+c)$

Use inverse operations and leave $a$ at one side-

Here, $2$ is being divided, so multiply both sides by $2$

$2b=h(a+c)$

$h$ is being multiplied so divide both sides by $h$

$\dfrac{2b}{h}=(a+c)$

$c$ is being added so subtract $c$ from both sides

$\dfrac{2b}{h}-c=a$