Решите пожалуйста)))

Решите задачу:

$\frac{x^{12}*x^{3}}{x^{13}}=\frac{x^{12+3}}{x^{13}}=x^{15-13}=x^{2} \\\\2^{2} =4\\\\\\\frac{x^{2}y^{3}}{4} :\frac{20x}{y}=\frac{x^{2}y^{3}}{4}*\frac{y}{20x}=\frac{x*y^{4}}{80}\\\\\frac{-1*3^{4}}{80}=-\frac{81}{80}=-1\frac{1}{80}=-1,0125\\\\\\(a^{2})^{3}:a^{5}=a^{6}:a^{5}=a^{6-5}=a, a=\frac{1}{2}\\\\\\\frac{2^{4}}{3^{3}} :\frac{2^{6}}{3^{5}} =\frac{2^{4}}{3^{3}}*\frac{3^{5}}{2^{6}}=\frac{3^{2}}{2^{2}}=\frac{9}{4}=2,25$