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

       = \(\dfrac{1}{3}\)- \(\dfrac{8}{15}\)-\(\dfrac{1}{7}\) + \(\dfrac{2}{3}\)+\(\dfrac{-7}{15}\)+\(\dfrac{6}{7}\)

       = \(\dfrac{1}{3}\)+\(\dfrac{2}{3}\)-\(\dfrac{8}{15}\)+\(\dfrac{-7}{15}\)-\(\dfrac{1}{7}\)+\(\dfrac{6}{7}\)

       = (\(\dfrac{1}{3}\)+\(\dfrac{2}{3}\))-(\(\dfrac{8}{15}\)+\(\dfrac{-7}{15}\))-(\(\dfrac{1}{7}\)+\(\dfrac{6}{7}\))

       = 1-15-1

       =-13

b)  B=0,25+\(\dfrac{3}{5}\)-(\(\dfrac{1}{8}\)-\(\dfrac{2}{5}\)+1\(\dfrac{1}{4}\))

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

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

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

       = \(\dfrac{-1}{2}\)+1-\(\dfrac{1}{8}\)

       = \(\dfrac{3}{8}\)