A=a+b+c+d÷4 for c
Assume A and a are different variables:
Cross multiply:
a + b + c + d = 4A
Subtract a, b, and d from each side:
a + b + c + d - (a + b + d) = 4A - (a + b + d)
Cancel the a + b + d on the left side
c = 4A - a - b - d
Assume A and a are different variables:
Cross multiply:
a + b + c + d = 4A
Subtract a, b, and d from each side:
a + b + c + d - (a + b + d) = 4A - (a + b + d)
Cancel the a + b + d on the left side
c = 4A - a - b - d