Odpowiedź :
a)
[tex]\frac{12}{20} = \frac{12:4}{20:4} = \boxed{\frac{3}{5}}[/tex]
b)
[tex]\frac{2}{7} = \frac{2\cdot3}{7\cdot3} = \boxed{\frac{6}{21}}\\\\\\\frac{3}{15} = \frac{3:3}{15:3} = \boxed{\frac{1}{5}}[/tex]
a)
[tex]\frac{12}{20} = \frac{12:4}{20:4} = \boxed{\frac{3}{5}}[/tex]
b)
[tex]\frac{2}{7} = \frac{2\cdot3}{7\cdot3} = \boxed{\frac{6}{21}}\\\\\\\frac{3}{15} = \frac{3:3}{15:3} = \boxed{\frac{1}{5}}[/tex]