1/6×2/5÷(5/6-3/4)
=1/15÷(10/12-9/12)
=1/15×12
=4/5
5/39×26/55÷(3/11)
=1/39×26/11×11/3
=2/3/3
=2/9
(11.4-4.2)×5/9
=7.2×5/9
=0.8×5
=4