Solve: S = n/2 (a+b) for b

b = - n / (2-S) - a

Step-by-step explanation:

S = n/2 (a+b)

divide both sides by (a+b)

S / (a+b) = n/2

flip the equation on the left (it is the same equation just negative)

- (a+b) / -S = n/2

divide both sides by - S

-a-b = n / (2-S)

add a to both sides

-b = n / (2-S) + a

flip the sign (multiply/divide by - 1)

b = - n / (2-S) - a