Question

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

Answer 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