\(\frac{x+8}{12}+\frac{x+9}{11}+\frac{x+10}{10}+3=0\)
\(\Rightarrow\left(\frac{x+8}{12}+1\right)+\left(\frac{x+9}{11}+1\right)+\left(\frac{x+10}{10}+1\right)=0\)\
\(\Rightarrow\frac{x+20}{12}+\frac{x+20}{11}+\frac{x+20}{10}=0\)\(\Leftrightarrow\left(x+20\right)\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)=0\)
\(\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)\ne0\Rightarrow x+20=0\Leftrightarrow x=0-20=-20\)
\(\frac{x+8}{12}+\frac{x+9}{11}+\frac{x+10}{10}+3=0\)
\(\Leftrightarrow\left(\frac{x+8}{12}+1\right)+\left(\frac{x+9}{11}+1\right)+\left(\frac{x+10}{10}+1\right)=0\)
\(\Leftrightarrow\frac{x+8+12}{12}+\frac{x+9+11}{11}+\frac{x+10+10}{10}=0\)
\(\Leftrightarrow\frac{x+20}{12}+\frac{x+20}{11}+\frac{x+20}{10}=0\)
\(\Leftrightarrow\left(x+20\right)\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)=0\)
Vì \(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\ne0\)
=> \(x+20=0\)
=> \(x=-20\)