a)
[tex]\it =\dfrac{1+2+3+\ ...\ +119}{120}=\dfrac{\dfrac{119\cdot120}{2}}{120}=\dfrac{\ \ 119\cdot120^{(120}}{2\cdot120}=\dfrac{119}{120}[/tex]
b)
[tex]\it =\dfrac{2(1+2+3+\ ...\ +24)}{50}=\dfrac{\not2\cdot\dfrac{24\cdot25}{\not2}}{50}=\dfrac{600}{50}=12[/tex]
