by N+F gives R(N+F)=F,which can b rewritten as RN+RF=F Subtracting RF from each side of RN+RF=F gives RN=F−RF, which can be factored as RN=F(1−R).Finally,dividing each side of RN=F(1-R) by 1−R express F in terms of the other variable:F=
RN
1−R
Subtracting RF from each side of RN+RF=F gives RN=F−RF, which can be factored