a: \(\frac{-3}{4}+\frac57+\frac{-1}{4}+\frac27+\frac{9}{24}\)
\(=\left(-\frac34-\frac14\right)+\left(\frac57+\frac27\right)+\frac38\)
\(=-1+1+\frac38=\frac38\)
b: \(\frac{-4}{5}\cdot\frac{7}{12}+\frac{-4}{3}\cdot\frac95-\frac{-4}{5}\cdot\left(-\frac16\right)\)
\(=-\frac45\left(\frac{7}{12}+\frac93+\frac16\right)=-\frac45\left(\frac{7}{12}+\frac{36}{12}+\frac{2}{12}\right)=-\frac45\cdot\frac{45}{12}=\frac{-9}{3}=-3\)
c: \(\left(\frac{2020}{4040}-\frac17\right)-\left(-\frac{3}{21}+\frac{7}{12}\right)-\frac{5}{12}\)
\(=\frac12-\frac17+\frac17-\frac{7}{12}-\frac{5}{12}=\frac12-\frac{12}{12}\)
\(=\frac12-1=-\frac12\)
d: \(\left|-\frac{15}{2}\right|+\frac{3}{18}-\left(-\frac{5}{15}\right)^2\)
\(=\frac{15}{2}+\frac16-\frac19=\frac{135}{18}+\frac{3}{18}-\frac{2}{18}=\frac{136}{18}=\frac{68}{9}\)
