7/15*14/9+23/15/9/14-14/9
=7/15x14/9+23/15x14/9-14/9
=(7/15+23/15-1)x14/9
=1x14/9
=14/9
15/4x=0.8:4/15
x=15/4x4/15÷0.8
x=5/4
2x:3.5=25%
x:1.75=25%
x=7/4x1/4
x=7/16
2*(x -2)+3*(4x-1)=18
2x-4+12x-3=18
2x+12x=18+7
14x=25
x=25/14
如果本题有什么不明白可以追问,