Zad. 1
P=\frac{1}{2}*a*h=0,5*7,8*6,9=26,91[cm^2]
Zad. 2
P=a*b=7\frac{1}{3}*3\frac{1}{7}=\frac{22*22}{3*7}=\frac{484}{21}=23\frac{1}{21}[cm^2]
Zad. 3
P=\frac{(a+b)*h}{2}=\frac{1}{2}*(7\frac{1}{2}+8\frac{1}{3})*2\frac{3}{4}=\frac{1}{2}*(7\frac{3}{6}+8\frac{2}{6})*\frac{11}{4}=
=\frac{1}{2}*15\frac{5}{6}*\frac{11}{4}=\frac{1}{2}*\frac{95}{6}*\frac{11}{4}=\frac{1045}{48}=21\frac{37}{48}[cm^2]