Original Equation:                     S/R + 5 = T/R

Currently, R only appears in the denominators of the two fractions.  In order to solve for R, you'll need to move R up so it no longer appears as a denominator.  To do this multiply both sides of the equation by R.

Mult. both sides by R:            R(S/R + 5) = R(T/R)

Distribute the R on the left:  R(S/R) + 5R = R(T/R)

Simplify:                                    S + 5R = T

From here, subtract S from both sides and continue solving for R by isolating the R on the left.

Multiply each term by R to clear the R from the denominator, then solve for R.