您好:
(1/3+2/5)÷4/15
=11/5÷4/15
=33/4
5/7×16.31-2.31÷7/5
=5/7x16.31-2.31x5/7
=5/7x(16.31-2.31)
=5/7x14
=10
4÷2/3-8÷1/12
=6-96
=-90
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(1/3+2/5)÷4/15
=11/15×15/4
=11/4
5/7×16.31-2.31÷7/5
=5/7×16.31-2.31×5/7
=(16.31-2.31)×5/7
=14×5/7
=10
4÷2/3-8÷1/12
=4×3/2-8×12
=6-84
=-78