[tex]\frac{3}{7}\;;\;\frac{4}{5}\;;\;\frac{11}{14}\;;\;\frac{19}{21}[/tex]
7 = 7
9 = 3²
14 = 2 * 7
21 = 3 * 7
c.m.m.m.c.= 2 * 3² *7 = 126
[tex]\frac{18*3}{18*7}=54 /126\;;
\frac{14*4}{14*9}=56 / 126\;;
\frac{9*11}{9*14}=99 / 126\;;
\frac{6*19}{6*21}=114 / 126\;;
[/tex]
