a) 4\frac{3}{5}+2 \frac{3}{4}=4\frac{12}{20}+2 \frac{15}{20}=6\frac{27}{20}=7\frac{7}{20}
b) 3 \frac{3}{8}-2 \frac{3}{4}=3 \frac{3}{8}-2 \frac{6}{8}=2 \frac{11}{8}-2 \frac{6}{8}=\frac{5}{8}
c) 2 \frac{2}{5}*3 \frac{3}{4}=\frac{12}{5}*\frac{5}{4}=\frac{12}{4}=3
d) \frac{5}{6}:7 \frac{1}{2}=\frac{5}{6}:\frac{15}{2}=\frac{5}{6}*\frac{2}{15}=\frac{5}{45}=\frac{1}{9}