\(a.\dfrac{75}{90}=\dfrac{75:15}{90:15}=\dfrac{5}{6}\)

\(b.\dfrac{36}{63}=\dfrac{36:9}{63:9}=\dfrac{4}{7}\)

\(c.\dfrac{80}{48}=\dfrac{80:16}{48:16}=\dfrac{5}{3}\)

a. \(\dfrac{21}{27}=\dfrac{21:3}{27:3}=\dfrac{7}{9};\dfrac{6}{18}=\dfrac{6:6}{18:6}=\dfrac{1}{3}\)

\(MSC=9\)

\(\Rightarrow\dfrac{1}{3}=\dfrac{1\times3}{3\times3}=\dfrac{3}{9}\)

\(\dfrac{7}{9}\) giữ nguyên phân số.

________

b. \(\dfrac{52}{72}=\dfrac{52:4}{72:4}=\dfrac{13}{18};\dfrac{5}{10}=\dfrac{5:5}{10:5}=\dfrac{1}{2}\)

\(MSC=18\)

\(\Rightarrow\dfrac{1}{2}=\dfrac{1\times9}{2\times9}=\dfrac{9}{18}\)

\(\dfrac{13}{18}\) giữ nguyên phân số.

Oki ạ.

2 và 4 nha bạn.

is not different