Solve for c A=(a+b+c+d)/4

$A = \frac{a + b + c + d}{4}$

Rewrite the equation as $\frac{a + b + c + d}{4} = A$ .

$\frac{a + b + c + d}{4} = A$

Multiply both sides of the equation by $4$ .

$4 \frac{a + b + c + d}{4} = 4 A$

Simplify the left side.

Cancel the common factor of $4$ .

Cancel the common factor.

$4 \frac{a + b + c + d}{4} = 4 A$

Rewrite the expression.

$a + b + c + d = 4 A$

Move all terms not containing $c$ to the right side of the equation.

Subtract $a$ from both sides of the equation.

$b + c + d = 4 A - a$

Subtract $b$ from both sides of the equation.

$c + d = 4 A - a - b$

Subtract $d$ from both sides of the equation.

$c = 4 A - a - b - d$