\(\frac{x+109}{91}+\frac{x+110}{90}-\frac{x+120}{80}-\frac{x+135}{65}=4\)
\(\left(\frac{x+109}{91}+1\right)+\left(\frac{x+110}{90}+1\right)+\left(\frac{-x+120}{80}+1\right)+\left(\frac{-x+135}{65}+1\right)=4+4\)
\(\frac{x+200}{91}+\frac{x+200}{90}-\frac{x+200}{80}-\frac{x+200}{65}=8\)
\(\left(x+200\right)\left(\frac{1}{91}+\frac{1}{90}-\frac{1}{80}-\frac{1}{65}\right)=8\)
chỉ làm tới đây được thôi bạn