\(a,\dfrac{7}{15}+\dfrac{4}{5}=\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{19}{15}\\ b,\dfrac{9}{13}\times\dfrac{4}{3}=\dfrac{3\times3\times4}{13\times3}=\dfrac{12}{13}\\ c,4-\dfrac{5}{6}:\dfrac{3}{4}=4-\dfrac{5}{6}\times\dfrac{4}{3}=4-\dfrac{10}{9}=\dfrac{36}{9}-\dfrac{10}{9}=\dfrac{26}{9}\)
a) \(\dfrac{7}{15}+\dfrac{4}{5}=\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{19}{15}\)
b) \(\dfrac{9}{13}\) x \(\dfrac{4}{3}=\dfrac{3x3x4}{13x3}=\dfrac{12}{13}\)
c) \(4-\dfrac{5}{6}:\dfrac{3}{4}=4-\dfrac{5}{6}\) x \(\dfrac{4}{3}=4-\dfrac{10}{9}=\dfrac{36}{9}-\dfrac{10}{9}=\dfrac{26}{9}\)