1
a)$\frac{7}{9}$ + $\frac{5}{12}$ - $\frac{3}{4}$
=$\frac{28}{36}$ + $\frac{15}{36}$ - $\frac{27}{36}$
=$\frac{4}{9}$
b)1,4 . $\frac{15}{49}$ . ($\frac{4}{5}$ + $\frac{2}{3}$):2$\frac{1}{5}$
=$\frac{7}{5}$ . ($\frac{4}{5}$ + $\frac{2}{3}$): $\frac{11}{5}$
=$\frac{7}{5}$ . $\frac{15}{49}$.$\frac{22}{15}$ : $\frac{11}{5}$
=$\frac{3}{7}$.$\frac{22}{15}$ :$\frac{11}{5}$
=$\frac{3}{7}$.$\frac{2}{3}$
=.$\frac{2}{7}$
