2/3 ÷8/9 ×(1-1/4)
=2/3 ÷8/9×3/4
=2/3 ×9/8×3/4
=3/4×3/4
=9/16
(1/2+1/3)÷2/5-3/4
=(3/6+2/6)÷2/5-3/4
=5/6÷2/5-3/4
=5/6×5/2-3/4
=25/12-9/12
=16/12
=4/3