4/9×2/3×99/8
＝4×2/3×11/8
=8/3×11/8
=11/3
24÷4/5÷3/8
=24×5/4×8/3
=24×40/12
=80
【1/6＋3/8】×24
=1/6×24+3/8×24
=4+9
=13
31×3/5+31÷5/2
=31×3/5+31×2/5
=31×（3/5+2/5）
=31
【3/4-1/12】×3/5
=【9/12-1/12】×3/5
=8/12×3/5
=2/3×3/5
=2/5