b: \(=\dfrac{15\left(1-\dfrac{1}{13}-\dfrac{1}{127}\right)}{81\left(1-\dfrac{1}{13}-\dfrac{1}{127}\right)}:\dfrac{115\left(1+\dfrac{1}{121}-\dfrac{1}{11}\right)}{16\left(1+\dfrac{1}{121}-\dfrac{1}{11}\right)}\)
=15/81:115/16
=16/621
d: =51(1/51+1/127-1/191-1/181)/23(1/51+1/127-1/191-1/181)
=51/23