7/25÷8/5+3/25×7/8
=7/25×5/8+7/25×3/8
=7/25×(5/8+3/8)
=7/25×1
=7/25
（1/36÷1/4+1/9）÷5/6
=（1/36×4+1/9）×6/5
=(1/9+1/9)×6/5
=2/9×6/5
=4/15