Answer:
A. a = 2s - b -c
Step-by-step 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.
[tex]s = \frac{a + b + c}{2}[/tex]
Multiply by 2 to get rid of the fraction.
[tex]s \cdot 2 = \frac{a + b + c}{2} \cdot 2[/tex]
On the right side the 2 cancels out:
[tex]s \cdot 2 = a + b + c[/tex]
On the right side next to a are still b and c. But we want a alone. Subtract b.
[tex]s \cdot 2 - b = a + b + c - b[/tex]
b - b on right side gives 0.
[tex]s \cdot 2 - b = a + c + 0[/tex]
The step above is usually skipped, because number + 0 = number.
[tex]s \cdot 2 - b = a + c[/tex]
Next to a there is still c. Subtract c.
[tex]s \cdot 2 - b - c = a + c - c[/tex]
c - c on the left is 0.
[tex]s \cdot 2 - b - c = a[/tex]
So our answer is:
[tex]s \cdot 2 - b - c = a[/tex]
It can be rewritten to (change sides):
[tex]a = s \cdot 2 - b - c[/tex]
And s · 2 can be rewritten to 2s:
[tex]a = 2s - b - c[/tex]
