a) \(\dfrac{5}{8}\) + \(\dfrac{3}{8}\) :\(\dfrac{2}{3}\) = \(\dfrac{5}{8}\) + \(\dfrac{3}{8}\) .\(\dfrac{3}{2}\) = \(\dfrac{5}{8}\) + \(\dfrac{9}{16}\) = \(\dfrac{10}{16}\) + \(\dfrac{9}{16}\) = \(\dfrac{19}{16}\)
b) \(\dfrac{1}{72}\) .\(\dfrac{144}{23}\) + \(\dfrac{1}{46}\) = \(\dfrac{2}{23}\) + \(\dfrac{1}{46}\) = \(\dfrac{4}{46}\) + \(\dfrac{1}{46}\) = \(\dfrac{5}{46}\)