tự làm

a)\(\frac{77}{24}\)=\(3\frac{5}{24}\)

b)=10

c)\(\frac{24}{35}\)

\(8\frac{7}{12}-5\frac{3}{8}=\frac{8.12+7}{12}-\frac{5.8+3}{8}=\frac{103}{12}-\frac{43}{8}=\frac{77}{24}\)

\(2\frac{9}{13}.3\frac{5}{7}=\frac{2.13+9}{13}.\frac{3.7+5}{7}=\frac{35}{13}.15=\frac{525}{13}\)

\(3\frac{19}{35}:5\frac{7}{42}=\frac{3.35+19}{35}:\frac{5.42+7}{42}=\frac{124}{35}:\frac{31}{6}=\frac{124}{35}.\frac{6}{31}=\frac{24}{35}\)

\(\frac{7}{19}\)x\(\frac{1}{3}\)+\(\frac{7}{19}\)x\(\frac{2}{3}\)=\(\frac{7}{19}\)x(\(\frac{1}{3}\)+\(\frac{2}{3}\))=\(\frac{7}{19}\)x1=\(\frac{7}{19}\)

\(\frac{7}{19}\)x \(\frac{1}{3}\)x \(\frac{7}{19}\)x \(\frac{2}{3}\)

= \(\frac{7}{19}\)x (\(\frac{1}{3}\)+ \(\frac{2}{3}\))

= \(\frac{7}{19}\)x 1

= \(\frac{7}{19}\)

Chúc bạn học tốt!

=7/9*[1/3+2/3]=7/9*1=7/9

a) \(\frac{3}{5}\times\frac{8}{27}\times\frac{5}{3}\)

\(=\left(\frac{3}{5}\times\frac{5}{3}\right)\times\frac{8}{27}\)

\(=1\times\frac{8}{27}\)

\(=\frac{8}{27}\)

b) \(\frac{7}{19}\times\frac{1}{3}+\frac{7}{19}\times\frac{2}{3}\)

\(=\frac{7}{19}\times\left(\frac{1}{3}+\frac{2}{3}\right)\)

\(=\frac{7}{19}\times1\)

\(=\frac{7}{19}\)

a) \(\left(\frac{3}{5}.\frac{5}{3}\right).\frac{8}{27}\)

=  \(1.\frac{8}{27}\)

=\(\frac{8}{27}\)

b) \(\frac{7}{19}.\left(\frac{1}{3}.\frac{2}{3}\right)\)

= \(\frac{7}{19}.\frac{2}{9}\)

=\(\frac{14}{81}\)

Không biết có đúng không? Tick mình nha !

3/4, 11/12, 19/18, 7/6 

(học tốt)

3/4 ; 11/12; 19/18; 7/6 nha

\(250\times12-\left(242+302\times2,5\right)\)

\(=3000-997\)

\(=2003\)

\(\frac{6}{19}< \frac{8}{25}< \frac{7}{19}\)

\(a=\frac12+\frac56+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}\)

\(=1-\frac12+1-\frac16+1-\frac{1}{12}+1-\frac{1}{20}+1-\frac{1}{30}+1-\frac{1}{42}+1-\frac{1}{56}\)

\(=7-\left(\frac12+\frac16+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\right)\)

\(=7-\left(1-\frac12+\frac12-\frac13+\frac13-\frac14+\frac14-\frac15+\frac15-\frac16+\frac16-\frac17+\frac17-\frac18\right)\)

\(=7-\left(1-\frac18\right)=7-\frac78=\frac{56}{8}-\frac78=\frac{49}{8}\)

Đề bài:
a = 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56

Giải:
Ta thấy mỗi phân số có tử số = mẫu số trừ 1
Vậy ta viết lại:

a = (2 - 1)/2 + (6 - 1)/6 + (12 - 1)/12 + (20 - 1)/20 + (30 - 1)/30 + (42 - 1)/42 + (56 - 1)/56
= 1 - 1/2 + 1 - 1/6 + 1 - 1/12 + 1 - 1/20 + 1 - 1/30 + 1 - 1/42 + 1 - 1/56
= 7 - (1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56)
= 7 - 3/2
= 11/2

Đáp số: 11/2