a) \(A=\left[\dfrac{2}{7}.\left(\dfrac{1}{4}-\dfrac{1}{3}\right)\right]:\left[\dfrac{2}{7}.\left(\dfrac{1}{3}-\dfrac{2}{3}\right)\right]=\left(\dfrac{1}{4}-\dfrac{1}{3}\right):\left(\dfrac{1}{3}-\dfrac{2}{5}\right)=1\dfrac{1}{4}\)

b) \(B=\dfrac{\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{2}{7}-\dfrac{1}{3}+\dfrac{2}{7}\right)}{\dfrac{1}{5}\left(\dfrac{2}{7}+\dfrac{1}{3}\right)-\dfrac{1}{3}\left(\dfrac{2}{7}+\dfrac{1}{3}\right)}=\dfrac{\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{1}{3}\right)}{\left(\dfrac{1}{5}-\dfrac{1}{3}\right).\left(\dfrac{2}{7}+\dfrac{1}{3}\right)}=1\dfrac{11}{52}\)

a) \(A=\dfrac{3}{5}.\dfrac{6}{7}+\dfrac{3}{7}.\dfrac{3}{5}-\dfrac{2}{7}.\dfrac{3}{5}=\dfrac{3}{5}\left(\dfrac{6}{7}+\dfrac{3}{7}-\dfrac{2}{7}\right)=\dfrac{3}{5}\)

b) \(B=\left(-13.\dfrac{2}{5}+\dfrac{-2}{9}.\dfrac{2}{5}+\dfrac{2}{5}.\dfrac{11}{9}\right).\dfrac{5}{2}=\left(-13-\dfrac{2}{9}+\dfrac{11}{9}\right).\dfrac{2}{5}.\dfrac{5}{2}=-13+\left(\dfrac{11}{9}-\dfrac{2}{9}\right)=-12\)

c) \(C=\left(\dfrac{-4}{5}+\dfrac{5}{7}\right).\dfrac{3}{2}+\left(\dfrac{-1}{5}+\dfrac{2}{7}\right)\dfrac{3}{2}=\left(\dfrac{-4}{5}+\dfrac{5}{7}+\dfrac{-1}{5}+\dfrac{2}{7}\right).\dfrac{3}{2}=\left(\left(\dfrac{-4}{5}+\dfrac{-1}{6}\right)\left(\dfrac{5}{7}\dfrac{2}{7}\right)\right).\dfrac{3}{2}=0\)

d) \(D=\dfrac{4}{9}:\left(\dfrac{1}{15}-\dfrac{10}{15}\right)+\dfrac{4}{9}\left(\dfrac{2}{22}-\dfrac{5}{22}\right)=\dfrac{4}{9}:\dfrac{-3}{5}+\dfrac{4}{9}:\dfrac{-3}{22}=\dfrac{4}{9}.\dfrac{-5}{3}+\dfrac{4}{9}.\dfrac{-22}{3}=\dfrac{4}{9}.\left(\dfrac{-5}{3}+\dfrac{-22}{3}\right)=\dfrac{4}{9}.\dfrac{-27}{3}=-4\)

a) P=\(\dfrac{2}{3}+\dfrac{1}{4}+\dfrac{3}{5}-\dfrac{7}{45}+\dfrac{5}{9}+\dfrac{1}{12}+\dfrac{1}{35}\)=\(\left(\dfrac{2}{3}+\dfrac{1}{4}+\dfrac{1}{12}\right)+\left(\dfrac{5}{9}+\dfrac{7}{45}\right)+\dfrac{3}{5}+\dfrac{1}{35}\)=\(1+\dfrac{4}{5}+\dfrac{3}{5}+\dfrac{1}{35}=2\dfrac{1}{35}\)

b)Q=\(\left(5-6-2\right)+\left(\dfrac{-3}{4}-\dfrac{7}{4}+\dfrac{5}{4}\right)+\left(\dfrac{1}{5}+\dfrac{8}{5}+\dfrac{16}{5}\right)=-\left(3+\dfrac{5}{4}+\dfrac{7}{5}\right)=\dfrac{-113}{20}\)

a) A=(\(\dfrac{1}{3}+\dfrac{2}{3}\)) - (\(\dfrac{8}{15}+\dfrac{7}{15}\)) + (\(\dfrac{-1}{7}+1\dfrac{1}{7}\))= 1-1+1=1

b) B=(0.25-\(1\dfrac{1}{4}\))+(\(\dfrac{3}{5}+\dfrac{2}{5}\))-\(\dfrac{1}{8}\)=(\(\dfrac{1}{4}-1-\dfrac{1}{4}\))+1-\(\dfrac{1}{8}\)=\(\dfrac{-1}{8}\)