A website uses the formula above to calculate a seller's rating, R, based on the number of favorable reviews, F, and unfavorable reviews, N. Which of the following expresses the number of favorable reviews in terms of the other variables?

F=RN/R-1

F=RN/1-R

F=N/1-R

F=N/R-1

The correct formula is

RN / (1-R) = F.

To solve for F, we start by multiplying by (N+F) to remove it from the denominator:

R (N+F) = F

Distributing, we have:

RN + RF = F

Subtracting RF to collect all of the F's on one side,

RN = F - RF

Factoring out F on the right hand side,

RN = F (1 - R)

Dividing both sides by (1-R),

RN / (1-R) = F