a) \(\dfrac{a}{b}=\dfrac{0.6\cdot100}{70}=\dfrac{60}{70}=\dfrac{6}{7}\)
b) \(\dfrac{a}{b}=\dfrac{0.2\cdot100}{12}=\dfrac{20}{12}=\dfrac{5}{3}\)
c) \(\dfrac{a}{b}=\dfrac{\dfrac{2}{3}\cdot100}{75}=\dfrac{200}{3}\cdot\dfrac{1}{75}=\dfrac{200}{225}=\dfrac{8}{9}\)
d) \(\dfrac{a}{b}=\dfrac{3}{10}:\dfrac{1}{3}=\dfrac{3}{10}\cdot3=\dfrac{9}{10}\)