\(P=\dfrac{2^{20}\cdot3^{10}+2^9\cdot2^{12}\cdot3^9}{15\cdot2^{18}\cdot3^8-2^{19}\cdot3^9}=\dfrac{2^{20}\cdot3^9\left(3+2\right)}{2^{18}\cdot3^9\cdot5-2^{19}\cdot3^9}\)
\(=\dfrac{2^{20}\cdot3^9\cdot5}{2^{18}\cdot3^9\left(5-2\right)}=4\cdot\dfrac{5}{3}=\dfrac{20}{3}\)