题目可以这样计算。
原式=(9/6-4/6)×1/2-(3/2×3/2-19/4)+(28/36-15/36)×3
=5/6×1/2-(9/4-19/4)+13/36×3
=5/12+30/12+13/12
=48/12
=4
(1又1/2-2/3)×1/2-(1又1/2÷2/3-4又3/4)+(7/9-5/12)÷1/3
=(3/2-2/3)×1/2-(3/2×3/2-19/4)+(7/9×3-5/12×3)
=(3/4-1/3)-(9/4-19/4)+(7/3-5/4)
=3/4-1/3-(-10/4)+7/3-5/4
=3/4+10/4-5/4-1/3+7/3
=2+2
=4