The value of r can be found as follow
We will use the relationship
[tex]RU=UA[/tex][tex]18-2r=4r[/tex]Collecting like terms
[tex]\begin{gathered} 2r+4r=18 \\ 6r=18 \end{gathered}[/tex]Divide both sides by 6
[tex]r=\frac{18}{6}=3[/tex]r=3
Answer = A
