0.75-8分之3）乘以9分之3除以5分之3=(3/8)*(3/9)*(5/3)=(3/8)*(5/9)=(1/8)*(5/3)=5/241-7分之5除以4分之5+2分之1=1-(5/7)*(4/5)+1/2=1-4/7+1/2=3/7+1/2=13/14
