[tex] \frac{28}{30} \div \frac{21}{25} = [/tex]
[tex] = \frac{28}{30} \times \frac{25}{21} = [/tex]
[tex] = \frac{7 \times 4}{5 \times 6} \times \frac{5 \times 5}{3 \times 7} = [/tex]
[tex] = \frac{2}{3} \times \frac{5}{3} = [/tex]
[tex] = \frac{10}{9} [/tex]