======================================
$\dfrac{2}{15}+\dfrac{2}{3}+\dfrac{7}{10}=$ $(mcm= 30)$
$= \dfrac{4+20+21}{30}=$
$= \dfrac{\cancel{45}^3}{\cancel{30}_2}=$ semplifica dividendo sopra e sotto per 15:
$= \dfrac{3}{2}$
$\dfrac{17}{24}+\dfrac{5}{8}+\dfrac{3}{5}=$ $(mcm= 120)$
$= \dfrac{85+75+72}{120}=$
$= \dfrac{\cancel{232}^{29}}{\cancel{120}_{15}}=$ semplifica dividendo sopra e sotto per 8:
$= \dfrac{29}{15}$