`(28^7 . 5^6 . 15^9)/(14^6 . 25^7 . 6^10)`
`=(2^{14}.7^7. 5^6 .5^9 .3^9)/(2^{6}.7^6. 5^14. 2^10. 3^10)`
`=(2^{14}.3^9. 5^{15}.7^7)/(2^{16}.3^{10}.7^6. 5^14)`
`=(5.7)/(2^2 .3 )`
`=35/12`

\(\dfrac{25}{28}:\dfrac{15}{14}\cdot\dfrac{6}{7}=\dfrac{25}{28}\cdot\dfrac{14}{15}\cdot\dfrac{6}{7}\)

\(=\dfrac{25}{15}\cdot\dfrac{14}{28}\cdot\dfrac{6}{7}=\dfrac{5}{3}\cdot\dfrac{1}{2}\cdot\dfrac{6}{7}\)

\(=\dfrac{5}{7}\)

5/7 nha bạn 

= 25/28x14/15x6/7

=15/21=5/7

\(\dfrac{tử số}{mẫu số}\)

\(\frac{25}{28}:\frac{15}{14}.\frac{6}{7}\)\(=\frac{25}{28}.\frac{14}{15}.\frac{6}{7}=\frac{5}{7}\)

\(\frac{4}{7}.\frac{5}{36}.\frac{21}{25}\)

\(=\frac{4.5.21}{7.36.25}\)

\(=\frac{4.5.7.3}{7.4.9.5.5}\)

\(=\frac{3}{9.5}=\frac{3}{3.3.5}=\frac{1}{15}\)

\(\frac{25}{28}:\frac{15}{14}.\frac{6}{7}\)

\(=\frac{25.14.6}{28.15.7}\)

\(=\frac{5.5.14.6}{28.5.3.7}\)

\(=\frac{5.6}{2.3.7}=\frac{5.2.3}{2.3.7}\)

\(=\frac{5}{7}\)

thank you bạn nam giải bài toán đầu tiên nha

a) \(\dfrac{7}{-25}+\dfrac{8}{25}=\dfrac{-7}{25}+\dfrac{8}{25}=\dfrac{1}{25}\)

\(\dfrac{4}{5}+\dfrac{4}{-18}=\dfrac{4}{5+\left(-18\right)}=\dfrac{4}{-13}=\dfrac{-4}{13}\)

\(\dfrac{7}{21}+\dfrac{9}{-36}=\dfrac{1}{3}+\dfrac{1}{-4}=\dfrac{1}{3+\left(-4\right)}=\dfrac{1}{-1}=1\)

b) \(\dfrac{12}{20}-\dfrac{2}{5}=\dfrac{12}{20}+\left(\dfrac{-2}{5}\right)=\dfrac{3}{5}+\dfrac{-2}{5}=\dfrac{3+\left(-2\right)}{5}=\dfrac{1}{5}\)

\(\dfrac{2}{3}-\dfrac{-5}{6}=\dfrac{2}{3}+\dfrac{5}{6}=\dfrac{4}{6}+\dfrac{5}{6}=\dfrac{9}{6}=\dfrac{3}{2}\)

\(6-\dfrac{3}{20}=6+\dfrac{-3}{20}=\dfrac{60}{60}+\dfrac{-9}{60}=\dfrac{51}{60}\)

c) \(\dfrac{2}{21}.\dfrac{-7}{3}=\dfrac{2.\left(-1\right)}{7.3}=\dfrac{-2}{21}\)

\(\dfrac{27}{28}.\left(-21\right)=\dfrac{27.\left(-21\right)}{28}=\dfrac{-567}{28}\)

\(\dfrac{-15}{7}.\dfrac{-14}{25}=\dfrac{-3.\left(-2\right)}{1.5}=\dfrac{6}{5}\)

15 - (-15 + 2) = 15 + 13 = 28

(-14) - (17 - 8) = -14 - 9 = -23

15 - (21- 7) = 15 - 14 = 1

34 + (-15) - 17 = 19 - 17 = 2

(-34) + (-12) + 18 = -46 + 18 = -28

27 - 15 - 19 = 12 - 19 = -7

34 - (-15) + 8 = 49 + 8 = 57

-37 + 13 - 25 = -24 - 25 = -49

40 - 17 + (-25) = 23 + (-25) = -2

16 + (-15) - 18 = 1 - 18 = -17

15 - 14 - 13 = 1 - 13 = -12

-27 + 15 - 17 = -12 - 17 = -29

34 - 71 = -37

28 - 125 = -97

13 + (-27) = -14

14 - (-34) = 48

28 - (-16) = 44

-15 - 8 = -23

-27 - 34 = -61

-25 - (-18) = -7

46 - 25 - (-25) = 21 + 25 = 46

-37 - (-24) = -13

46 - (-15) = 61

-26 - 6 + 7 = -32 + 7 = -25

@linhcute