Những cái như 1 3/5 là hỗn số nha 

a)\(\frac{1}{2}:\frac{1}{5}+\frac{1}{3}:\frac{1}{5}+\frac{1}{6}:\frac{1}{5}\)

=\(\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{6}\right):\frac{1}{5}\)

=\(1:\frac{1}{5}\)

=5

b)\(\frac{1515\text{×}161616}{151515\text{×}1616}\)

=1

a) 2/3 : 3/5 × 5/7 : 2/3

= 2/3 × 5/3 × 5/7 × 3/2 

= 25/21

b) 1 1/2 × 1 1/3 × 1 1/18 × 1 1/15 × 1 1/24 × 1 1/35

= 3/2 × 4/3 × 19/18 × 16/15 × 25/24 × 36/35

= 2 × 152/35 × 15/14

= 304/35 × 15/14

= 152/7

Tui rất cảm ơn b nhiều :))))

Giải đấy đủ giúp mình với 

a: =8/15x1/4=2/15

b: \(=\dfrac{5}{3}\cdot\dfrac{4}{5}\cdot\dfrac{6}{7}=\dfrac{24}{21}=\dfrac{8}{7}\)

c: \(=\dfrac{2}{5}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\)

1) 3/9 + 5/9 = 8/9

2) 1/2 x 2/3 x 3/4 x 4/5

= 1/5

(1-1/2)×(1-1/3)×(1-1/4)×(1-1/5)×1-1/6=1/2×2/3×3/4×4/5×5/6=1/6

\(a.\left(\dfrac{2}{5}.\dfrac{5}{2}\right).\dfrac{10}{21}=1.\dfrac{10}{21}=\dfrac{10}{21}\)

\(\dfrac{1}{2}.4+\dfrac{3}{4}.4=2+3=5\)

a tính bằng cách là

( 2/5 x 5/2 ) x 10/21 

= 1 x 10/21 

10/21

b tính bằng cách là

1/2 + ( 3/4 x 4)

=1/2 x 12/4 rút gọn là 1/2 x 3

= 3/2

\(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot\dfrac{3}{4}\cdot\dfrac{4}{5}\\ =\dfrac{1}{5}\)

"Và" ở đây nghĩa là sao bạn nhỉ?