(1)[3/4]-[5/8]
=[6/8]-[5/8]
=[1/8];
(2)[1/6]+[2/9]+[5/6]+[3/9]
=([1/6]+[5/6])+([2/9]+[3/9])
=1+[5/9]
=1[5/9];
(3)[1/12]×5×[12/17]
=[1/12]×[12/17]×5
=[1/17]×5
=[5/17];
(4)[3/4]×[4/5]+[1/3]×[1/2]
=[3/5]+[1/6]
=[23/30].
(1)[3/4]-[5/8]
=[6/8]-[5/8]
=[1/8];
(2)[1/6]+[2/9]+[5/6]+[3/9]
=([1/6]+[5/6])+([2/9]+[3/9])
=1+[5/9]
=1[5/9];
(3)[1/12]×5×[12/17]
=[1/12]×[12/17]×5
=[1/17]×5
=[5/17];
(4)[3/4]×[4/5]+[1/3]×[1/2]
=[3/5]+[1/6]
=[23/30].