Question

Given the following formula, solve for a.

Answer 1

A. a = 2s - b -c

Explanation:

Rearrange the equation in a way that you have only a on one side. When solving equations you can add, subtract, multiply or divide by the same number/variable/expression on the both sides.

`s = (a + b + c)/(2)`

Multiply by 2 to get rid of the fraction.

`s \cdot 2 = (a + b + c)/(2) \cdot 2`

On the right side the 2 cancels out:

`s \cdot 2 = a + b + c`

On the right side next to a are still b and c. But we want a alone. Subtract b.

`s \cdot 2 - b = a + b + c - b`

b - b on right side gives 0.

`s \cdot 2 - b = a + c + 0`

The step above is usually skipped, because number + 0 = number.

`s \cdot 2 - b = a + c`

Next to a there is still c. Subtract c.

`s \cdot 2 - b - c = a + c - c`

c - c on the left is 0.

`s \cdot 2 - b - c = a`

So our answer is:

`s \cdot 2 - b - c = a`

It can be rewritten to (change sides):

`a = s \cdot 2 - b - c`

And s · 2 can be rewritten to 2s:

`a = 2s - b - c`