1又4分之17乘以(2又3分之2-0.75)+15又2分之1除以17分之21
=21/4*(8/3-3/4)+31/2/(21/17)
=21/4*8/3-21/4*3/4+31/2*17/21
=14-63/16+527/42
=14*336/336-63*21/336+527*8/336
=4704/336-1323/336+4216/336
=(4704-1323+4216)/336
=7600/336
=475/21