【1又2/3-(1/3-1/6+5/12)×2.4】÷4
=【1又2/3-(1/3×2.4-1/6×2.4+5/12×2.4)】÷4
=【1又2/3-(0.8-0.4+1)】÷4
=【1又2/3-1.4】÷4
=4/15÷4
=1/15