1. (a+5)/(6-2a)=(a+5)/(2*(3-a)).
2. 54/(5a+a²)=54/(a*(5+a)=54/(a*(a+5).
3. ((a+5)/(2*(3-a)))*(54/(a*(a+5))=(54*(a+5)/(2*(3-a)*a*(a+5))=27/(a*(3-a)).
4. 3a/(a-3)+27/(a*(3-a))=3a/(a-3)-27/(a*(a-3))=(3a*a-27)/(a*(a-3))=
=(3a²-27)/(a*(a-3))=3*(a²-9)/(a*(a-3))=3*(a-3)*(a+3)/(a*(a-3))=3*(a+3)/a.