(17分之1+19分之1)*17*19
=1/17*17*19+1/19*17*19
=19+17
=36
(3分之1-8分之1)*24
=1/3*24-1/8*24
=8-3
=5
49分之13*21+13*49分之28
=13/49*21+13/49*28
=13/49*(21+28)
=13/49*49
=13
(17分之1+19分之1)*17*19
=1/17*17*19+1/19*17*19
=19+17
=36
(3分之1-8分之1)*24
=1/3*24-1/8*24
=8-3
=5
49分之13*21+13*49分之28
=13/49*21+13/49*28
=13/49*(21+28)
=13/49*49
=13