Đáp án:

`(x+3)/50+(x+4)/49+(x+5)/48=(x+9)/44+(x+11)/42+(x+13)/40`

`(x+3)/50+1+(x+4)/49+1+(x+5)/48+1=(x+9)/44+1+(x+11)/42+1+(x+13)/40+1`

`(x+53)/50+(x+53)/49+(x+53)/48=(x+53)/44+(x+53)/42+(x+53)/40`

`(x+53)/50+(x+53)/49+(x+53)/48-((x+53)/44+(x+53)/42+(x+53)/40)=0`

`(x+53)/50+(x+53)/49+(x+53)/48-(x+53)/44-(x+53)/42-(x+53)/40=0`

`(x+53)*(1/50+1/49+1/48-1/44-1/42-1/40)=0`

Mà `1/50+1/49+1/48-1/44-1/42-1/40 \ne 0`

`=>` `x+53=0`

`=>` `x=-53`

Vậy `x=-53`