a)
3,75 + 4\frac{ 1}{6} - 2\frac{2}{3} =
3,75 + 4\frac{ 1}{6} - 2\frac{2}{3}=3\frac{3}{4}+4\frac{2}{12}-2\frac{8}{12}=
=3\frac{9}{12}+4\frac{2}{12}-2\frac{8}{12}=7\frac{11}{12}-2\frac{8}{12}=
=5\frac{3}{12}=5\frac{1}{4}