(4/15+2/3):2/5=(4/15+10/15):2/5=14/15:2/5=14/15*5/2=7/3=2 1/3
(4/9+1/6)*9/11=(8/18+3/18)*9/11=11/18*9/11=1/2
8/11*(5/6-3/8)=8/11*(20/24-9/24)=8/11*11/24=1/3
3/5:(4/5-1/2)=3/5:(8/10-5/10)=3/5:3/10=3/5*10/3=2
3/8*(7/12+3/4)=3/8*(7/12+9/12)=3/8*16/12=2/4=1/2