\(\dfrac{3}{5}+\left(-\dfrac{3}{7}\right)+\left(-\dfrac{3}{5}\right)=\left(\dfrac{3}{5}+-\dfrac{3}{5}\right)+\dfrac{3}{7}=0+\dfrac{3}{7}=\dfrac{3}{7}.\)
\(b,\left(-\dfrac{7}{4}.\dfrac{3}{8}+-\dfrac{7}{4}.\dfrac{5}{8}\right)+\dfrac{7}{15}\div-\dfrac{14}{5}\)
\(=\left(-\dfrac{7}{4}.\left(\dfrac{3}{8}+\dfrac{5}{8}\right)\right)+-\dfrac{5}{2}\)
\(=\left(-\dfrac{7}{4}.1\right)+-\dfrac{5}{2}\)
\(=-\dfrac{7}{4}+-\dfrac{5}{2}=-\dfrac{17}{4}\)
\(c,\left(\sqrt{0,25}-1.2\right)\div1\dfrac{1}{20}-\left(-\dfrac{5}{2}\right)^2-\left|-\dfrac{1}{12}\right|\)
\(=\left(0,5-1,2\right)\div1\dfrac{1}{20}-\dfrac{25}{4}-\dfrac{1}{12}\)
\(=-0,7\div\dfrac{21}{20}-\dfrac{25}{4}-\dfrac{1}{12}\)
\(=-\dfrac{2}{3}-\dfrac{25}{4}-\dfrac{1}{12}=-7\)