` \frac{x+1}{2019} + \frac{x+2}{2018} + \frac{x+3}{2017} = \frac{x+10}{2010} + \frac{x+11}{2009} + \frac{x+12}{2008} `
` <=> \frac{x+1}{2019} + 1 + \frac{x+2}{2018} + 1 + \frac{x+3}{2017} + 1 = \frac{x+10}{2010} + 1 + \frac{x+11}{2009} + 1 + \frac{x+12}{2008} + 1 `
` <=> \frac{x+2020}{2019} + \frac{x+2020}{2018} + \frac{x+2020}{2017} = \frac{x+2020}{2010} + \frac{x+2020}{2009} + \frac{x+2020}{2008} `
` <=> (x+2020)(1/2019 + 1/2018 + 1/2017 + 1/2010 + 1/2009 + 1/2008) = 0 `
` <=> x + 2020 = 0 `
` <=> x = -2020 `
Vậy ` x = -2020 `
