Выполните действие:
m+4/5m-10 + 3-m/4m-8

(m+4)/(5m-10) + (3-m)/(4m-8)=(m+4)/5(m-2) + (3-m)/4(m-2)=

=(4(m+4)+5(3-m))/20(m-2)=(4m+16+15-5m)/20(m-2)=

=(31-m)/(20m-40)