Question

i dont understand this

Solve the equation S/R + 3 = T/R for R in terms of S and T.

Answer 1

@jbug55:
\[\frac{ S }{ R } + 3 = \frac{ T }{ R }\]

In the above eqn. we have to make R the subject of the formula expressed in terms of S and T
SO:
\[\frac{ S + 3R }{ R } = \frac{ T }{ R}\]
Now Transposing:
\[S + 3R = \frac{ T }{ R } \times R\]
\[S + 3R = T\]
\[3R = T -S\]
\[R = \frac{ T -S }{ 3 }\]

Answer 2

I have to point out one tiny constraint to @Adjax's solution - given the original problem R cannot equal zero. Which means in the final solution we have to add the constraint.
\[T \neq S\]