c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)

\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)

\(=1-2=-1\)

Giải:

a)-1/12+4/3=-1/12+16/12=15/12=5/4

b)(-4/14-3/15)-(1/5-20/35-(-1)).7

=-17/35-22/35.7

=-17/35-22/5

=-171/35

c)3/5+-5/20+30/75+-7/4

=3/5+-1/4+2/5+-7/4

=(3/5+2/5)+(-1/4+-7/4)

=1+-2

=-1

d)5/6.-12/14+7/13

=-5/7+7/13

=-16/91

e)2/-9-5/-36-1/4

=-1/12-1/4

=-1/3

f)2/23+-5/12+7/18+21/23+-7/12

=(2/23+21/23)+(-5/12+-7/12)+7/18

=1+-1+7/18

=7/18

\(\frac{7}{18}.\left(\frac{-12}{23}-\frac{4}{15}\right)+\frac{7}{18}.\left(\frac{8}{30}+\frac{35}{23}\right)\)

\(=\frac{7}{18}.\left(\frac{-12}{23}-\frac{4}{15}\right)+\frac{7}{18}.\left(\frac{4}{15}+\frac{35}{23}\right)\)

\(=\frac{7}{18}.\left(\frac{-12}{23}-\frac{4}{15}+\frac{4}{15}+\frac{35}{23}\right)\)

\(=\frac{7}{18}.[\left(\frac{-12}{23}+\frac{35}{23}\right)+\left(\frac{-4}{15}+\frac{4}{15}\right)]\)

\(=\frac{7}{18}.1+0\)

\(=\frac{7}{18}\)

_Chúc bạn học tốt_

a)-35.12-8-35=-35(12+8)=-35.20=-700

b)23.(-7)-7.5+(-18).7=-7(23+59+18)=-7.100=-700

c)115-(-12+29)=115+12-29=98

d)\(3\left(-7\right)^2+5\left(-4\right)^3=3.7^2-5.4^3=3.49-5.64=147-320-173\)

\(a,-35.12-8.35\)

\(=\left(-35\right)\left(12+8\right)\)

\(=-700\)

\(b,-23.7-7.59-18.7\)

\(=7\left(-23-59-18\right)\)

\(7.\left(-100\right)=-700\)

\(b,115-\left(-12+29\right)\)

\(=115+12-29\)

\(=98\)

\(c,3.\left(-7\right)^2+5.\left(-4\right)^3\)

\(=3.49-5.64\)

\(=147-320\)

\(=-173\)

a, (-17)  + 21 + 79 + 17

= (-17 + 17) + (21 + 79)

= 0 + 100

= 100

b, 40 + 22 + (-16)  + (-44)

= 40 + {(-16) + (-44} + 22

= 40 - 60 + 22

= - 20 + 22

= 2 

c, (-12) + (-47) + (-28) + 47

=  - (12 + 28) + (-47 + 47)

= - 40 + 0
= - 40

d, (- 5) + (-3) + 35 + (-17)

= (-5 + 35) - (3 + 17)

=  30 - 20

=  10 

e, 21.23 - 3.7.(-17)

= 21.23 + 21.17

= 21.(23 + 17)

= 21. 40

= 840 

Tách từng câu ra giùm, như này ai giải nổi:)))))