[tex]a) \\ \frac{ \frac{1}{3}*2+ \frac{1}{6}*3+ \frac{3}{8}*4}{2+3+4}=\frac{ \frac{2}{3}+\frac{1}{2}+ \frac{3}{2}}{9}=\frac{ \frac{4}{6}+\frac{3}{6}+ \frac{9}{6}}{9}=\frac{ \frac{4+3+9}{6}}{9}= \frac{16}{6*9}= \frac{8}{3*9}=\frac{8}{27}[/tex]
[tex]b) \\ \frac{0,5*3+1,12*4+3,2*5+4*8}{3+4+5+8}=\frac{1,5+4,48+16+32}{18}= \\ =\frac{5,98+48}{18}=\frac{53,98}{18}=\frac{26,99}{9}=2,99(8)[/tex]
