3 ×17 + 3 × 25 - 3 × 2 = 3 × (17 + 25 – 2) = 3 × 40 = 120

3x(17+25-2)=3x40=120

a) \(\dfrac{2}{7}+\dfrac{4}{7}=\dfrac{2+4}{7}=\dfrac{6}{7}\)

b) \(\dfrac{23}{13}+\dfrac{8}{13}=\dfrac{23+8}{13}=\dfrac{31}{13}\)

c) \(\dfrac{27}{125}+\dfrac{16}{125}=\dfrac{27+16}{125}=\dfrac{43}{125}\)

a)\(\dfrac{2}{7}\) + \(\dfrac{4}{7}\) =  \(\dfrac{6}{7}\)  

b)\(\dfrac{23}{13}\) + \(\dfrac{8}{13}\) = \(\dfrac{31}{13}\)          

c)\(\dfrac{27}{125}\) + \(\dfrac{16}{125}\) = \(\dfrac{43}{125}\)

a, \(\left(\frac{4}{9}.\frac{3}{7}\right).\frac{7}{4}=\frac{4}{9}\left(\frac{3}{7}.\frac{7}{4}\right)=\frac{4}{9}.\frac{3}{4}=\frac{3}{9}=\frac{1}{3}\)

b, \(\left(\frac{6}{5}.\frac{4}{5}\right).\frac{25}{16}=\frac{6}{5}\left(\frac{4}{5}.\frac{25}{16}\right)=\frac{6}{5}.\frac{5}{4}=\frac{6}{4}=\frac{3}{2}\)

c, \(\left(\frac{7}{8}.\frac{16}{9}\right).\frac{3}{14}=\frac{7}{8}\left(\frac{16}{9}.\frac{3}{14}\right)=\frac{7}{8}.\frac{8}{21}=\frac{7}{21}=\frac{1}{3}\)

a, $\left(\frac{4}{9}.\frac{3}{7}\right).\frac{7}{4}=\frac{4}{9}\left(\frac{3}{7}.\frac{7}{4}\right)=\frac{4}{9}.\frac{3}{4}=\frac{3}{9}=\frac{1}{3}$

b, $\left(\frac{6}{5}.\frac{4}{5}\right).\frac{25}{16}=\frac{6}{5}\left(\frac{4}{5}.\frac{25}{16}\right)=\frac{6}{5}.\frac{5}{4}=\frac{6}{4}=\frac{3}{2}$

c, $\left(\frac{7}{8}.\frac{16}{9}\right).\frac{3}{14}=\frac{7}{8}\left(\frac{16}{9}.\frac{3}{14}\right)=\frac{7}{8}.\frac{8}{21}=\frac{7}{21}=\frac{1}{3}$

( 4/9 x 3/7 ) x 7/4 = 4/9 x ( 3/7 x 7/4 ) =4/9 x 21/28 = 84/252

( 6/5 x 4/5 ) x 25/16 = ( 25/16 x 4/5 ) x 6/5 = 100/80 x 6/5 = 600/400

a: \(5+\dfrac{3}{2}=\dfrac{10}{2}+\dfrac{3}{2}=\dfrac{10+3}{2}=\dfrac{13}{2}\)

\(\dfrac{3}{4}+2=\dfrac{3}{4}+\dfrac{8}{4}=\dfrac{3+8}{4}=\dfrac{11}{4}\)

\(\dfrac{8}{9}+3=\dfrac{8}{9}+\dfrac{27}{9}=\dfrac{8+27}{9}=\dfrac{35}{9}\)

b: \(1-\dfrac{1}{2}=\dfrac{2}{2}-\dfrac{1}{2}=\dfrac{2-1}{2}=\dfrac{1}{2}\)

\(5-\dfrac{7}{3}=\dfrac{15}{3}-\dfrac{7}{3}=\dfrac{15-7}{3}=\dfrac{8}{3}\)

\(\dfrac{11}{2}-3=\dfrac{11}{2}-\dfrac{6}{2}=\dfrac{11-6}{2}=\dfrac{5}{2}\)

a: 7/4=28/16

15/16=15/16

b: 1/8=3/24

2/3=16/24

5/2=60/24

c: 2/7=8/28

9/4=63/28

5/28=5/28

a)\(28/16 và 15/16\)

b)\(3/24; 16/24; 60/24\)

c)\(8/28; 63/28; 5/28\)nhé 

a)=3.7/5=21/5

b)=4.3=12

c)=5.6=30

mình ko viết đề bài

A ) 3: 5/7 = 3/1 :5/7 = 3/1 x 7/5 = 21/5 

B) 4: 1/3 = 4/1 : 1/3 = 4/1 x 3/1 = 12/1 = 12

C) 5 : 1/6 = 5/1 :1/6 = 5/1 x 6/1 = 30 /1 =30

Đúng 100000000000% luôn , chúc bạn học tốt ^_^

a: \(\dfrac{1}{8}+\dfrac{5}{8}=\dfrac{1+5}{8}=\dfrac{6}{8}=\dfrac{3}{4}\)

b: \(\dfrac{1}{15}+\dfrac{4}{15}=\dfrac{1+4}{15}=\dfrac{5}{15}=\dfrac{1}{3}\)

c: \(\dfrac{5}{9}+\dfrac{7}{9}=\dfrac{5+7}{9}=\dfrac{12}{9}=\dfrac{4}{3}\)

d: \(\dfrac{23}{100}+\dfrac{27}{100}=\dfrac{23+27}{100}=\dfrac{50}{100}=\dfrac{1}{2}\)

a) $\frac{1}{8}+\frac{5}{8}=\frac{1+5}{8}=\frac{6}{8}=\frac{3}{4}$

b) $\frac{1}{15}+\frac{4}{15}=\frac{1+4}{15}=\frac{5}{15}=\frac{1}{3}$

c) $\frac{5}{9}+\frac{7}{9}=\frac{5+7}{9}=\frac{12}{9}=\frac{4}{3}$

d) $\frac{23}{100}+\frac{27}{100}=\frac{23+27}{100}=\frac{50}{100}=\frac{1}{2}$