4/15÷(6/7×(4/9+1/6))= 4/15÷(6/7×4/9+ 6/7 x1/6)【小括号内的分数约分】= 4/15÷(8/21+ 1/7 )【小括号内的分数通分】=4/15 ÷11/(3x7)=4/15 x (3x7)/11【约分】=28/55
