1999又1999/2000乘以13
=(2000-1/2000)*13
=13-13/200
=12又1987/2000
(8又2/5-4/5除以2/21)乘以4/23
=(8.4-0.8x21/2)*4/23
=0
7.68-(7/12+2又8/25-3又5/12)
=7+34/50-(2+8/25-2-5/6)
=7+34/50-(48-125)/150
=7+102/150+77/150
=7+179/150
=8+29/150
1999又1999/2000乘以13
=(2000-1/2000)*13
=13-13/200
=12又1987/2000
(8又2/5-4/5除以2/21)乘以4/23
=(8.4-0.8x21/2)*4/23
=0
7.68-(7/12+2又8/25-3又5/12)
=7+34/50-(2+8/25-2-5/6)
=7+34/50-(48-125)/150
=7+102/150+77/150
=7+179/150
=8+29/150