Bài 1: 

a: x+1/2=5/6

nên x=5/6-1/2=1/3

b: x+1/4=3/4

nên x=3/4-1/4=2/4=1/2

c: x+3/10=1/2

nên x=1/2-3/10=5/10-3/10=1/5

d: x+1/4=3/8

nên x=3/8-1/4=3/8-2/8=1/8

TOT LAM

b. 5/6 + ( 5/6 -1/4 )= 5/6 + 7/12= 17/12= 1/5/12

a, 7/20 - ( 5/8-2/5 )= 7/20-9/40=1/8

c. 9/10-( 2/5 + 3/10 ) + 7/20= 9/10- 7/10+7/20=2/10+ 7/20= 11/20

Là sao!!!!!???????!!!!!???

địt con mẹ mày lên

\(\dfrac{1}{3}\)-\(\dfrac{2}{15}\)+\(\dfrac{14}{15}\)=\(\dfrac{3}{15}\)-\(\dfrac{2}{15}\)+\(\dfrac{14}{15}\)

=\(\dfrac{13}{15}\)

\(\dfrac{3}{5}\)+4-\(\dfrac{6}{7}\)=\(\dfrac{3}{5}\)+\(\dfrac{20}{5}\)-\(\dfrac{6}{7}\)=\(\dfrac{23}{5}\)-\(\dfrac{6}{7}\)=\(\dfrac{161}{35}\)-\(\dfrac{30}{35}\)=\(\dfrac{131}{35}\)

ai giúp mình với :)

Bài 1: Tính
a, 1/2 x 2/3 x 3/4 = 1/4
b, 7/8 x 8/9 x 9/10 = 7/10
c, 5/14 x 7/15 x 28/7 = 2/3
d, 2 x 1/2 x 3 x 1/3 x 4 x 1/4 x 5 x 1/5 = 1
Bài 2: Tính
a, 7/20 - ( 5/8 - 3/5 ) = 7/20 - 1/40 = 14/40 - 1/40 = 13/40
b, 5/6 + ( 5/9 - 1/4 ) = 5/6 + 11/36 = 30/36 + 11/36 = 41/36
c, 9/10 - ( 2/5 + 3/10 ) + 7/20 = 9/10 - 7/10 + 7/20 = 2/10 + 7/20 = 4/20 + 7/20 = 11/20.
Bài 3: Tìm x:
a, 1/2 + x = 5/6
x = 5/6 - 1/2
x = 1/3
b, 5/6 - x = 1/3
x = 5/6 - 1/3
x = 1/2
c, x - 1/mấy vậy bạn
d, 1/3 x x = 1/6
x = 1/6 : 1/3
x = 1/2

A) \(\frac{4}{5}+\frac{5}{4}-2=\frac{16}{20}+\frac{25}{20}-\frac{40}{20}\)

\(=\frac{1}{20}\)

B) \(3-\frac{2}{3}-\frac{3}{2}=\frac{18}{6}-\frac{4}{6}-\frac{9}{6}\)

\(=\frac{5}{6}\)

C) \(\frac{7}{8}-\left(\frac{1}{4}+\frac{2}{5}\right)=\frac{7}{8}-\frac{13}{20}\)

\(=\frac{35}{40}-\frac{26}{40}=\frac{9}{40}\)

D) \(\frac{9}{10}-\left(\frac{2}{5}+\frac{3}{10}\right)+\frac{7}{10}=\frac{9}{10}-\frac{7}{10}+\frac{7}{10}\)

\(=\frac{9}{10}\)