C1
a\(\dfrac{7}{5}+\dfrac{4}{5}=\dfrac{11}{5}\)
b \(\dfrac{2}{3}-\dfrac{3}{5}=\dfrac{10}{15}-\dfrac{9}{15}=\dfrac{1}{15}\)
c \(\dfrac{7}{6}\times\dfrac{5}{2}=\dfrac{35}{12}\)
d \(\dfrac{1}{2}:\dfrac{2}{5}=\dfrac{1}{2}\times\dfrac{5}{2}=\dfrac{5}{4}\)
C2
\(\dfrac{25}{135}=\dfrac{5}{27}\)
\(\dfrac{125}{100}=\dfrac{5}{4}\)