(1⼀15+1⼀21)×105 45÷5⼀7÷7⼀8 8⼀13÷7-1⼀7×6⼀13 1⼀5×5⼀8-1⼀5÷8⼀3 3⼀5÷5⼀8+2⼀5÷5⼀8简便运算

(1/15+1/21)×105
=（1/15）*（15*7）+（1/21）*（21*5）
=7+5
=12
45÷5/7÷7/8
=5*9*（7/5）*（8/7）
=9*8
=72
8/13÷7-1/7×6/13
=8/13*（1/7）-6/13*（1/7）
=（8/13-6/13）*（1/7）
=2/13*1/7
=2/91
1/5×5/8-1/5÷8/3
=1/5*5/8-1/5*3/8
=1/5*（5/8-3/8）
=1/5*1/4
=1/20
3/5÷5/8+2/5÷5/8
=（3/5+2/5）*（8/5）
=1*8/5
=8/5
x-1/2x=5/8
1/2x=5/8
x=5/8*2
x=5/4
4/5x÷2=7/16
4/5x=7/16*2
x=7/8*5/4
x=35/32
1/4x+1/3x=5/18
7/12x=5/18
x=5/18*12/7
x=10/21
1/8x÷3/10=5/18
1/8x=5/18*3/10
x=1/12*8
x=2/3
4/5x-3/4x=25
(16/20-15/20)*x=25
x=25/(1/20)
x=500

(1/15+1/21)×105=7+5=12
45÷5/7÷7/8 =45*7/5*8/7 =45*8/5=72
8/13÷7-1/7×6/13 =(8-6)/(13*7)=2/91
1/5×5/8-1/5÷8/3=5/40-3/40=2/40=1/20
3/5÷5/8+2/5÷5/8=(3/5+2/5)÷5/8 =8/5
x-1/2x=5/8 , x=5/4
4/5x÷2=7/16 , 2/5 x= 7/16, x=35/32
1/4x+1/3x=5/18 , 7/12 x = 5/18, x=10/21
1/8x÷3/10=5/18 , 1/8 x =5/18*3/10, x=2/3
4/5x-3/4x=25, (16-15)/20 x =25, x=500

(1/15+1/21)×105
=1/15×105+1/21×105
=7+5
=12

45÷5/7÷7/8
=45×7/5×8/7
=9×8
=72

8/13÷7-1/7×6/13
=8/13*1/7-1/7*6/13
=1/7*(8/13-6/13)
=1/7*2/13
=2/91

1/5×5/8-1/5÷8/3
=1/5×5/8-1/5×3/8
=1/8-3/40
=5/40-3/40
=2/40
=1/20

3/5÷5/8+2/5÷5/8
=3/5*8/5+2/5*8/5
=8/5*(3/5+2/5)
=8/5*1
=8/5

x-1/2x=5/8
1/2x=5/8
x=5/8*2
x=5/4

4/5x÷2=7/16
4/5x=7/16*2
x=7/8*5/4
x=35/32

1/4x+1/3x=5/18
7/12x=5/18
x=5/18*12/7
x=10/21

1/8x÷3/10=5/18
1/8x=5/18*3/10
x=1/12*8
x=2/3

4/5x-3/4x=25
(16/20-15/20)*x=25
x=25/(1/20)
x=500

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