\(A=\dfrac{72^3.54^2}{108^4}=\dfrac{\left(2^3.3^2\right)^3.\left(2.3^3\right)^2}{\left(2^2.3^3\right)^4}=\dfrac{2^9.3^6.2^2.3^6}{2^8.3^{12}}=\dfrac{2^{11}.3^{12}}{2^8.3^{12}}=2^3=8\)
\(B=\dfrac{3^{11}.11+3^{10}.5}{3^{10}.\left(11+5\right)}=\dfrac{3^{10}\left(3.11+5\right)}{3^{10}\left(11+5\right)}=\dfrac{38}{16}=\dfrac{19}{8}\)