9979-3050-9978+3051+x=3

=>2+x=3

=>x=3-2

=>x=1

\(\dfrac{72\overline{abc}}{\overline{abc}}=76\\ =>\dfrac{72000}{\overline{abc}}+\dfrac{\overline{abc}}{\overline{abc}}=76\\ =>\dfrac{72000}{\overline{abc}}+1=76\\ =>\dfrac{72000}{\overline{abc}}=75\\ =>\overline{abc}=72000:75=960\)

$72abc:abc=76$

$\Rightarrow 72000+abc=76\times abc$

$\Rightarrow 72000=76\times abc-abc$

$\Rightarrow 72000=abc\times (76-1)$

$\Rightarrow abc\times 75=72000$

$\Rightarrow abc=72000:75$

$\Rightarrow abc=960$

Vậy $abc=960$

\(\dfrac{2}{10}.x+\dfrac{3}{10}.x=2\)

\(x.\left(\dfrac{2}{10}+\dfrac{3}{10}\right)=2\)

\(x.\dfrac{5}{10}=2\)

\(x=2:\dfrac{5}{10}\)

\(x=4\)

\(\dfrac{2}{10}\times x+\dfrac{3}{10}\times x=2\\ =>x\times\left(\dfrac{2}{10}+\dfrac{3}{10}\right)=2\\ =>x\times\dfrac{1}{2}=2\\ =>x=2:\dfrac{1}{2}=4\)

2029-(x-2)=12

= x - 2 = 2029 - 12

= x - 2 = 2017

= x = 2017 + 2

= x = 2019

\(2029-\left(x-2\right)=12\)

\(\left(x-2\right)=2029-12\)

\(x-2=2017\)

\(x=1008,5\)

\(\dfrac{23}{6}\times\dfrac{5}{3}=\dfrac{23\times5}{6\times3}=\dfrac{115}{18}\)

23/6×5/3

= 23 x 5/ 6 x 3

= 115 /18

\(\dfrac{3}{2}+\dfrac{7}{3}=\dfrac{3.3}{2.3}+\dfrac{7.2}{3.2}\\ =\dfrac{9}{6}+\dfrac{14}{6}=\dfrac{9+14}{6}\\ =\dfrac{23}{6}\)

3/2+7/3 ( quy đồng lên mẫu số chung là 6)

= 9/6 + 14/6

= 9+14/6

= 23/6 

2/3×5/7+5/7×2/3+2/3×3/7

= 2/3 x ( 5/7 + 5/7 + 3/7)

= 2/3 x 13/7

= 2x13/3x7

= 26/21

2/3×5/7+5/7×2/3+2/3×3/7 

5/7 x ( 2/3+2/3+2/3)

5/7 x 6/3

30/21