r = 1 -4/9 -r +7/18
18r = 18 -8 -18r + 7
36r = 17
r = 17/36
\(r=1-\left(\dfrac{4}{9}+r-\dfrac{7}{18}\right)\)
\(\Rightarrow r=1-\dfrac{4}{9}-r-\dfrac{7}{18}\)
\(\Rightarrow r=1-\dfrac{8}{18}-\dfrac{7}{18}-r\)
\(\Rightarrow r=1-\dfrac{15}{18}-r\)
\(\Rightarrow r=\dfrac{3}{18}-r\)
\(\Rightarrow r+r=\dfrac{3}{18}\)
\(\Rightarrow2r=\dfrac{3}{18}\)
\(\Rightarrow r=\dfrac{1}{3}\)
\(R=1-\left(\dfrac{4}{9}+r-\dfrac{7}{18}\right)\)
=> \(R=1-\dfrac{4}{9}-r-\dfrac{7}{18}\)
=> \(R=1-\dfrac{8}{18}-\dfrac{7}{18}-r\)
=> \(R=1-\dfrac{15}{18}-r\)
=> \(R=\dfrac{3}{18}-r\)
=> \(R+R\)\(=\dfrac{3}{18}\)
=> \(2R=\dfrac{3}{18}\)
=> \(R=\dfrac{1}{3}\)