a; \(\dfrac{9}{27}\) + \(\dfrac{7}{-49}\)

= \(\dfrac{1}{3}\) - \(\dfrac{1}{7}\)

= \(\dfrac{7}{21}\) - \(\dfrac{3}{21}\)

= \(\dfrac{4}{21}\)

b; - \(\dfrac{12}{10}\) + \(\dfrac{-25}{30}\)

   =  - \(\dfrac{6}{5}\) - \(\dfrac{5}{6}\)

   = -\(\dfrac{36}{30}\) - \(\dfrac{25}{30}\)

  = \(\dfrac{-61}{30}\) 

c; \(\dfrac{-20}{35}\) + \(\dfrac{-16}{-24}\)

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

= - \(\dfrac{12}{21}\) + \(\dfrac{14}{21}\)

=  \(\dfrac{2}{21}\)

d; - \(\dfrac{21}{77}\) + \(\dfrac{10}{-35}\)

 = - \(\dfrac{3}{11}\) - \(\dfrac{2}{7}\)

 = - \(\dfrac{21}{77}\) -  \(\dfrac{22}{77}\)

= - \(\dfrac{43}{77}\)

\(\frac{2130-15}{3550-25}=\frac{2115}{3525}=\frac{3}{5}\)

680 × 274 : 20 - 136

= 186320 : 20 -136

= 9316 - 136

= 9180

915 + 3550 : 25 + 554

= 915 + 142 + 554

= 1057 +554

=1611

83489 + 75 × 30

= 83489 + 2250

=85739

k mk nha bao ngan

= 9180.

= 1611.

= 85739.

680 × 274 : 20 - 136 = 186320 : 20 - 136 = 9316 - 136 = 9180

915 + 3550 : 25 + 554 = 915 + 142 + 554 = 1057 + 554 = 1611

83489 + 75 × 30 = 83489 + 2250 = 85739

6450+3550=10000 nha Trần Khánh Linh

6450 + 3550 = 10000 tink nhé

10000

\(x+3841:167=3550\)
\(x+23=3550\)
\(x=3550-23\)
\(x=3527\)

`x+3841:167=3550`

`=>x+23=3550`

`=>x=3550-23`

`=>x=3527`

\(x+3831:167=3550\)

\(x+23=3550\)

\(x=3550-23\)

\(\Rightarrow x=3527\)

=367 nhé

duyệt nha