4-9/15÷9/5-2/3
=4-9/15*5/9-2/3
=4-5/15-2/3
=4-(1/3+2/3)
=4-1
=3
（28+2/7×7/8）×1/4
=(28+1/4)*1/4
=28*1/4+1/4*1/4
=7+1/16
=7又1/16
12×（2/11-1/12）×11
=12*2/11*11-12*1/12*11
=24-11
=13
5/6+9/8×1/6×8/9
=5/6+1/6
=1
5－（13/5×5/26+1/4）
=5-（1/2+1/4）
=5-3/4
=4又1/4
（3/8+1/27）×8+19/27
=3/8*8+1/27*8+19/27
=3+（8/27+19/27）
=3+1
=4