To compare two fraction they have to have either the same numerator or denominator.
From two fractions with same nominator the one is bigger, which has smaller denominator.
From two fractions with the same denominator the one is bigger, which has bigger nominator.
[tex]\frac{5}{7}=\frac{50}{70}[/tex]
[tex]\frac{7}{10}=\frac{49}{70}[/tex]
That means that [tex]\frac{5}{7}[/tex] is greater than [tex]\frac{7}{10}[/tex]
[tex]\frac{13}{15}=\frac{65}{75}[/tex]
[tex]\frac{21}{25}=\frac{63}{75}[/tex]
That means that [tex]\frac{13}{15}[/tex] is greater than [tex]\frac{21}{25}[/tex]