\(\dfrac{2}{5}\cdot\dfrac{3}{7}-\dfrac{10}{7}+\dfrac{3}{7}\cdot\dfrac{3}{5}=\dfrac{3}{7}\cdot\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{10}{7}=\dfrac{3}{7}\cdot\dfrac{5}{5}-\dfrac{10}{7}=\dfrac{3}{7}\cdot1-\dfrac{10}{7}=\dfrac{3}{7}-\dfrac{10}{7}=-\dfrac{7}{7}=-1\)