39×9/14÷13/14÷18
=39÷18x9/14x14/13
= 2x9/13
=18/13
9/20×1/2+19/20÷2
=9/20×1/2+19/20x1/2
=（9/20+19/20）x1/2
=28/20x1/2
=7/10
（1/4+1/3÷1/2）÷1/5
=（1/4+2/3）÷1/5
= 1/4x5+2/3x5
=5/4+10/3
=55/12