Millä luvulla murtoluku on lavennettu?

a. [[$^{)}\frac{2}{3} = \frac{10}{15}$]]

b. [[$^{)}\frac{3}{4} = \frac{12}{16}$]]

c. [[$^{)}\frac{3}{6} = \frac{9}{18}$]]

d. [[$^{)}\frac{2}{3} = \frac{14}{21}$]]