\(B=\dfrac{4^6\cdot9^5+6^9\cdot120}{-8^4\cdot3^{12}+6^{11}}\\ =\dfrac{2^{12}\cdot3^{10}+2^9\cdot3^9\cdot3\cdot5\cdot2^3}{-2^{12}\cdot3^{12}+2^{11}\cdot3^{11}}\\ =\dfrac{2^{12}\cdot3^{10}+2^{12}\cdot3^{10}\cdot5}{-2^{12}\cdot3^{12}+2^{11}\cdot3^{11}}\\ =\dfrac{2^{12}\cdot3^{10}\cdot\left(1+5\right)}{2^{11}\cdot3^{11}\cdot\left(-2\cdot3+1\right)}\\ =\dfrac{2\cdot6}{3\cdot\left(-5\right)}\\ =\dfrac{12}{-15}\\ =\dfrac{-4}{5}\)