28×1⼀7+3⼀5÷3脱式计算

脱式计算,能简便要简便.
3/5×1/5÷3/5
=3/5÷3/5×1/5
=1/5
2/7-5/8×2/7
=(1-5/8)×2/7
=3/8×2/7
=3/28
1/4÷2/3+2/3÷4
=3/2÷4+2/3÷4
=(3/2+2/3)÷4
=13/6÷4
=13/24
1/3÷1/5+4/5
=5/3+4/5
=37/15
[1-(1/4+3/8)]÷1/4
=(1-5/8)×4
=3/8×4
=3/2
4/9×3/16+5/12
=1/12+5/12
=1/2
3/9-1/3×3/9
=(1-1/3)×1/3
=2/9
解方程
1/2X÷1/4=8
1/2x=2
x=4
1/4X+2/3=3
1/4x=3-2/3
1/4x=7/3
x=28/3
1/3X+1/2X=5
5/6x=5
x=6
2/5X+1/3×6=4
2/5x=4-2
2/5x=2
x=5
2/7X=1/2×3/14
2/7x=3/28
x=3/8
4.5X+X=11/17
5.5x=11/17
x=2/17
X-1/12X=22
11/12x=22
x=24