[2×（-1/2）²-3²×（-1/3）³]÷[1-（-1/2）³]

[2×（-1/2）²-3²×（-1/3）³]÷[1-（-1/2）³]
[2×（-1/2）²-3²×（-1/3）³]÷[1-（-1/2）³]

[2×（-1/2）²-3²×（-1/3）³]÷[1-（-1/2）³]
[2×（-1/2）²-3²×（-1/3）³]÷[1-（-1/2）³]
=[2×(1/4)-9×(-1/27)]÷[1-(-1/8)]
=(1/2+1/3)÷(1+1/8)
=(5/6)÷(9/8)
=20/27