2/9+1/4÷2/5+3/8
=2/9+1/4×5/2+3/8
=2/9+5/8+3/8
=2/9+(5/8+3/8)
=2/9+1
=1·2/9
=11/9
2/3+（4/7-1/2）×1/12
=2/3+(4/7-1/2)×1/12
=2/3+4/7×1/12-1/2×1/12
=2/3+1/21-1/24
=14/21+1/21-1/24
=15/21-1/24
=5/7-1/24
=120/168-7/168
=113/168
2/3+3/4x=1/6
3/4x=1/6-2/3
3/4x=1/6-4/6
3/4x=-1/2
x=-1/2×4/3
x=-2/3
1/2x÷1/5=3/5
1/2x=3/5×5
1/2x=3
x=3×2
x=6
5x-3/5=16/15
5x=16/15+3/5
5x=16/15+9/15
5x=25/15
5x=5/3
x=5/3×1/5
x=1/3