$\dfrac{x-2}{98} + \dfrac{x-199}{99} = \dfrac{x}{100} + \dfrac{x-201}{101}$
$\left(\dfrac{x-2}{98} - 1\right) + \left(\dfrac{x-199}{99} + 1\right) = \left(\dfrac{x}{100} - 1\right) + \left(\dfrac{x-201}{101} + 1\right)$
$\dfrac{x-100}{98} + \dfrac{x-100}{99} = \dfrac{x-100}{100} + \dfrac{x-100}{101}$
$\dfrac{x-100}{98} + \dfrac{x-100}{99} - \dfrac{x-100}{100} - \dfrac{x-100}{101} = 0$
$(x-100)\left(\dfrac{1}{98} + \dfrac{1}{99} - \dfrac{1}{100} - \dfrac{1}{101}\right) = 0$
Vì $\dfrac{1}{98} + \dfrac{1}{99} - \dfrac{1}{100} - \dfrac{1}{101} \neq 0$
$x-100 = 0$
$x = 100$