Solve the equation $\displaystyle \frac{{4}}{{R}}+\frac{{4}}{{S}}=\frac{{1}}{{T}}$ for $\displaystyle {R}$ in terms of $\displaystyle {S}$ and $\displaystyle {T}$.

$\displaystyle {R}=$ Preview Question 6  

Enter your answer as a simplified rational expression, i.e. your answer should not be in the form of a complex rational expression.