в). (3х*(х+у)/2у*(2х+3а)) * ((2х+3а)/2а*(х+у)=3х/4ау

г).  ((с-d)/c*(c+d)-c/d*(c+d) : (d^2/c*(c-d)*(c+d) + 1/(c+d))=

(cd-d^2-c^2/cd*(c+d)) : (d^2+c^2-cd/c*(c-d)*(c+d)=

(cd-d^2-c^2/cd*(c+d)) : (-(cd-d^2-c^2)/c*(c-d)*(c+d))= -c*(c-d)/cd