[(6a-24)/(2a2-5a+12)][(4a2-9)/(15a2)]=[(6a-24)/(15a2)][(4a2-9)/(2a2+5a-12)].
Some factorisation is possible:
6a-24=6(a-4); 4a2-9=(2a-3)(2a+3); 2a2+5a-12=(a+4)(2a-3).
(6a-24)/(15a2)=6(a-4)/(15a2)=(6/15)(a-4)/a2=⅖(a-4)/a2;
(4a2-9)/(2a2+5a-12)=(2a-3)(2a+3)/(a+4)(2a-3)=(2a+3)/(a+4).
So we end up with:
⅖(a-4)(2a+3)/(a2(a+4)) or 2(a-4)(2a+3)/(5a2(a+4)).