[tex]24)\ \ = \dfrac{2009-1}{2008\cdot2009}=\dfrac{2008}{2008\cdot2009} =\dfrac{1}{2009}[/tex]
26)
[tex]= \left(\dfrac{1}{90}\cdot\dfrac{45}{1}+\dfrac{1}{60}\cdot\dfrac{60}{1}\right):\dfrac{3}{2}=\left(\dfrac{1}{2}+1\right):\dfrac{3}{2} =\dfrac{3}{2}:\dfrac{3}{2} =1 \in\mathbb{N}[/tex]
