(1/15+1/21)×10545÷5/7÷7/88/13÷7-1/7×6/131/5×5/8-1/5÷8/33/5÷5/8+2/5÷5/8简便运算方程x-1/2x=5/84/5x÷2=7/161/4x+1/3x=5/181/8x÷3/10=5/184/5x-3/4x=25

Question

(1/15+1/21)×105 45÷5/7÷7/8 8/13÷7-1/7×6/13 1/5×5/8-1/5÷8/3 3/5÷5/8+2/5÷5/8简便运算
方程 x-1/2x=5/8 4/5x÷2=7/16 1/4x+1/3x=5/18 1/8x÷3/10=5/18 4/5x-3/4x=25

Answer 1

(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