Răspuns :

[tex] \frac{3}{7} = \frac{a}{21} [/tex]

[tex]a = \frac{3 \times 21}{7} = 9[/tex]

[tex] \frac{b + 1}{3} = \frac{4}{6} [/tex]

[tex]b + 1 = \frac{3 \times 4}{6} = 2[/tex]

[tex]b = 1[/tex]

COROANA?