Salutare!
[tex]\bf \dfrac{13}{39} +\dfrac{105}{42}+\dfrac{70}{100}=[/tex]
[tex]\bf \dfrac{\not13}{\not39} +\dfrac{\not105}{\not42}+\dfrac{\not70}{\not100}=[/tex]
[tex]\bf \dfrac{1}{3} +\dfrac{5}{2}+\dfrac{7}{10}=[/tex]
[tex]\bf \dfrac{1\cdot10}{3\cdot10} +\dfrac{5\cdot 15}{2\cdot15}+\dfrac{7\cdot3}{10\cdot3}=[/tex]
[tex]\bf \dfrac{10}{30} +\dfrac{75}{30}+\dfrac{21}{30}=[/tex]
[tex]\bf \dfrac{10+75+21}{30}=[/tex]
[tex]\bf \dfrac{106}{30}=[/tex]
[tex]\bf \dfrac{\not106}{\not30}=[/tex]
[tex]\boxed{\bf \dfrac{53}{15}}[/tex]
