3. Zadatak

Brojnik lijeve strane ima vrijednost:

$$(1+2007)+(3+2005)+\cdots+(1003+1005)=2008\cdot502.$$

Nazivnik lijeve strane ima vrijednost:

$$2\cdot(1+2+3+\cdots+1003+1004)=2\cdot\frac{1004}{2}\cdot1005=1004\cdot1005.$$

Jednadžba prelazi u:

$$\begin{gathered}\frac{2008\cdot502}{1004\cdot1005}=\frac x{2010}\\\frac{1004}{1005}=\frac x{2010}\\\frac{2008}{2010}=\frac x{2010}\\x=2008\end{gathered}$$