a.
\(=\left(\dfrac{12}{15}+\dfrac{10}{15}\right)\times5-\dfrac{5}{7}\)
\(=\dfrac{22}{15}\times5-\dfrac{5}{7}=\dfrac{22}{3}-\dfrac{5}{7}=\dfrac{154}{21}-\dfrac{15}{21}=\dfrac{139}{21}\)
a) \(\left(\dfrac{4}{5}+\dfrac{2}{3}\right):\dfrac{1}{5}-1,4.\left(-\dfrac{5}{7}\right)^2\)
\(=\dfrac{22}{15}:\dfrac{1}{5}-\dfrac{7}{5}.\dfrac{25}{49}\\ =\dfrac{22}{3}-\dfrac{5}{7}=\dfrac{139}{21}\)
b) \(\dfrac{-3}{11}.\dfrac{4}{9}+\dfrac{-3}{11}.\dfrac{5}{9}+1\dfrac{3}{11}\)
\(=\dfrac{-3}{11}\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+1+\dfrac{3}{11}\\ =-\dfrac{3}{11}+1+\dfrac{3}{11}=1\)
c) \(25\%-2\dfrac{1}{4}+2,8.\left(-\dfrac{15}{14}\right)\)
\(=\dfrac{1}{4}-\dfrac{9}{4}+\dfrac{14}{5}.\dfrac{-15}{14}\\ =-2+\left(-3\right)=-5\)
d) \(\left(34,72+32,28\right):5-\left(57,25-36,05\right):2\)
\(=67:5-21,2:2\)
\(=13,4-10,6=2,8\)
