Suma: $-2,75+3\frac{1}{3}=-2\frac{3}{4}+3\frac{1}{3}=-\frac{11}{4}+\frac{10}{3}=-\frac{33}{12}+\frac{40}{12}=\frac{7}{12}$

Różnica:   $3\frac{1}{3}-\left(-2,75\right)=3\frac{1}{3}+2\frac{3}{4}=\frac{10}{3}+\frac{11}{4}=\frac{40}{12}+\frac{33}{12}=\frac{73}{12}$