x:2/5=16
x=16*2/5
x=32/5
50%x-40=96/(1/2)
0.5x-40=96*2
0.5x=96*2-40
0.5x=152
x=304
1600÷(1-60%)=4000个
87/88*89
=87/88*(88+1)
=87/88*88+87/88*1
=87+87/88
=87又87/88
12*(5/4-5/6)/(5/3)
=12*(5/4-5/6)*3/5
=12*5*(1/4-1/6)*3/5
=36*(1/4-1/6)
=36*1/4-36*1/6
=9-6
=3
1/12-1/6+11/12-5/6
=1/12+11/12-1/6-5/6
=1/12+11/12-(1/6+5/6)
=1-1
=0
45*[8/15-(1/5+1/6)]
=45*[8/15-1/5-1/6]
=45*8/15-45*1/5-45*1/6
=24-15-15*1/2
=9-15/2
=3/2