你分数的分子分母写反了吧?
8/5,应该是5/8(8分之5吧)其他的也这样
1.
(5/8+5/6)×4/25
=5/8×4/25+5/6×4/25
=1/10+2/15
=3/30+4/30
=7/30
2.
(5/6-2/3)×9/10
=(5/6-4/6)×9/10
=1/6×9/10
=3/20
3.
1-7/9÷7/8
=1-7/9×8/7
=1-8/9
=1/9
你分数的分子分母写反了吧?
8/5,应该是5/8(8分之5吧)其他的也这样
1.
(5/8+5/6)×4/25
=5/8×4/25+5/6×4/25
=1/10+2/15
=3/30+4/30
=7/30
2.
(5/6-2/3)×9/10
=(5/6-4/6)×9/10
=1/6×9/10
=3/20
3.
1-7/9÷7/8
=1-7/9×8/7
=1-8/9
=1/9