Răspuns :
[tex]\dfrac{10}{20}+\dfrac{11}{33}+\dfrac{12}{72}=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}= \dfrac{3+2+1}{6}=\dfrac{6}{6}=\boxed{1}[/tex]
10 / 20 + 11 / 33 + 12 / 72 =
= 1 / 2 + 1 / 3 + 1 / 6
= 3 / 6 + 2 / 6 + 1 / 6
= 5 / 6 + 1 / 6
= 6 / 6
= 1