A.5/15 = 1/3 và 9/18 = 1/2
B.7/21 = 1/3 và 3/15= 1/5
a) \(\dfrac{5}{15}=\dfrac{5:5}{15:5}=\dfrac{1}{3};\dfrac{9}{18}=\dfrac{9:9}{18:9}=\dfrac{1}{2}\)
b) \(\dfrac{7}{21}=\dfrac{7:7}{21:7}=\dfrac{1}{3};\dfrac{3}{15}=\dfrac{3:3}{15:3}=\dfrac{1}{5}\)
\(a,\dfrac{5}{15}=\dfrac{5:5}{15:5}=\dfrac{1}{3};\dfrac{9}{18}=\dfrac{9:9}{18:9}=\dfrac{1}{2}\)
\(b,\dfrac{7}{21}=\dfrac{7:7}{21:7}=\dfrac{1}{3};\dfrac{3}{15}=\dfrac{3:3}{15:3}=\dfrac{1}{5}\)