\(A=\dfrac{1+4+7+8+5}{45}+\dfrac{1+2+3}{15}=\dfrac{5}{9}+\dfrac{2}{5}=\dfrac{43}{45}\)
\(B=\dfrac{1-2+3+4-5+6-7}{28}=0\)
\(A=\dfrac{1}{45}+\dfrac{2}{45}+\dfrac{1}{15}+\dfrac{4}{45}+\dfrac{1}{9}+\dfrac{2}{15}+\dfrac{7}{45}+\dfrac{8}{45}+\dfrac{1}{5}\)
\(A=\dfrac{1}{45}+\dfrac{2}{45}+\dfrac{3}{45}+\dfrac{5}{45}+\dfrac{6}{45}+\dfrac{7}{45}+\dfrac{8}{45}+\dfrac{9}{45}\)
\(A=\dfrac{1+2+3+5+5+6+7+8+9}{45}=\dfrac{46}{45}\)
\(B=\dfrac{1}{28}+\dfrac{-1}{14}+\dfrac{3}{28}+\dfrac{1}{7}+\dfrac{-5}{28}+\dfrac{6}{28}+\dfrac{3}{14}+\dfrac{-1}{4}\)
\(B=\dfrac{1}{28}+\dfrac{-2}{28}+\dfrac{3}{28}+\dfrac{4}{28}+\dfrac{-5}{28}+\dfrac{6}{28}+\dfrac{-7}{28}\)
\(B=\dfrac{1+\left(-2\right)+3+4+\left(-5\right)+6+\left(-7\right)}{28}=0\)
