27/15 + 6/8 =51/20
19/24 + 7/18 = 85/72
2/9 - 1/6 = 1/18
8/15 -1/3 = 1/5

e: \(D=\dfrac{-10}{12}-\dfrac{7}{12}-\dfrac{4}{12}=\dfrac{-21}{12}=-\dfrac{7}{4}\)

f: \(F=\dfrac{-27}{36}+\dfrac{12}{36}+\dfrac{10}{36}=\dfrac{-5}{36}\)

g: \(G=\dfrac{209}{99}+\dfrac{36}{99}+\dfrac{66}{99}=\dfrac{311}{99}\)

h: \(H=\dfrac{10}{24}-\dfrac{42}{24}+\dfrac{3}{24}=-\dfrac{29}{24}\)

\(D=\dfrac{-5}{6}+\dfrac{-7}{12}-\dfrac{1}{3}=-\dfrac{7}{4}\)

\(F=\dfrac{-3}{4}+\dfrac{1}{3}-\dfrac{-5}{18}=-\dfrac{5}{36}\)

\(G=\dfrac{19}{9}-\dfrac{-4}{11}+\dfrac{2}{3}=\dfrac{311}{99}\)

\(H=\dfrac{5}{12}+\dfrac{-7}{4}-\dfrac{1}{-8}=-\dfrac{29}{24}\)

1: \(\dfrac{1}{2}+\dfrac{9}{10}+\dfrac{5}{6}-\dfrac{11}{14}-\dfrac{1}{3}+\dfrac{-4}{35}\)

\(=\left(\dfrac{1}{2}+\dfrac{5}{6}-\dfrac{1}{3}\right)+\dfrac{9}{10}-\left(\dfrac{11}{14}+\dfrac{4}{35}\right)\)

\(=\dfrac{3+5-2}{6}+\dfrac{9}{10}-\dfrac{55+8}{70}\)

\(=1+\dfrac{9}{10}-\dfrac{9}{10}\)

=1

a: \(\frac23+\left(\frac57+\frac{-2}{3}\right)\)

\(=\frac23+\frac57-\frac23\)

\(=\frac57\)

b: \(\left(-\frac14+\frac58\right)+\frac{-3}{8}\)

\(=\frac{-2}{8}+\frac58+\frac{-3}{8}\)

=0

c: \(\frac75\cdot\frac{8}{19}+\frac75\cdot\frac{12}{19}-\frac75\cdot\frac{1}{19}\)

\(=\frac75\left(\frac{8}{19}+\frac{12}{19}-\frac{1}{19}\right)\)

\(=\frac75\cdot\frac{19}{19}=\frac75\)

d: \(6\frac{3}{10}-\left(3\frac47+2\frac{3}{10}\right)\)

\(=6+\frac{3}{10}-3-\frac47-2-\frac{3}{10}\)

\(=1-\frac47=\frac77-\frac47=\frac37\)

e: \(\left(31,12-5,97\right)-\left(-68,88+4,03\right)\)

=31,12-5,97+68,88-4,03

=100-10

=90

f: \(3,7\cdot\left(-10,56\right)+3,7\cdot110,56\)

\(=3,7\cdot\left(-10,56+110,56\right)\)

\(=3,7\cdot100=370\)

1/ \(\left(\dfrac{2021}{2020}+\dfrac{2020}{2021}\right).\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)\)

=\(\left(\dfrac{2021}{2020}+\dfrac{2020}{2021}\right).0\)

=\(0\)

mink chịu bài này nó rất khó

1. A

2. C

3. C

a) \(=\dfrac{157}{8}.\dfrac{12}{7}-\dfrac{61}{4}.\dfrac{12}{7}=\dfrac{12}{7}\left(\dfrac{157}{8}-\dfrac{61}{4}\right)=\dfrac{12}{7}.\dfrac{35}{8}=\dfrac{15}{2}\)

b) \(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}\div\dfrac{1}{5}+\dfrac{3}{5}.\dfrac{1}{3}=\dfrac{1}{3}\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{2}{15}.5=\dfrac{1}{3}.1-\dfrac{2}{3}=\dfrac{1}{3}-\dfrac{2}{3}=-\dfrac{1}{3}\)

c) \(=-\dfrac{80}{9}\)

d) \(=-\dfrac{1}{6}\)