$\frac{5}{18}+\frac{7}{18}=\frac{5+7}{18}=\frac{12}{18}=\frac{12:6}{18:6}=\frac{2}{3}$

$\frac{5}{12}+\frac{4}{12}=\frac{5+4}{12}=\frac{9}{12}=\frac{9:3}{12:3}=\frac{3}{4}$

$2\frac{15}{56}+4\frac{13}{56}=(2+4)+\frac{15+13}{56}=6\frac{28}{56}=6\frac{28:28}{56:28}=6\frac{1}{2}$

$7\frac{47}{48}-<!--\; -\; -->3\frac{17}{48}=(7-<!--\; -\; -->3)+\frac{47-<!--\; -\; -->17}{48}=4\frac{30}{48}=4\frac{30:6}{48:6}=4\frac{5}{8}$