One year later,
You have not understood my wrong answer!
[tex]6 \dfrac{1}{3} +4 \dfrac{3}{4}+3 \dfrac{7}{12} \\
=(6+ \dfrac{1}{3} )+(4+ \dfrac{3}{4})+(3+ \dfrac{7}{12} )\\\\
=(6+4+3)+( \dfrac{1}{3} + \dfrac{3}{4} + \dfrac{7}{12} )\\\\
=13+ \dfrac{4+9+7}{12} =13 \dfrac{20}{12} =13+1+ \dfrac{8}{12} \\\\
=14+ \dfrac{2}{3} =14 \dfrac{2}{3}
[/tex]
Is it more clear?