[tex] \frac{2}{9} de81 \\ 81 \div 9 = 9 \\ 9 \times 2 = 18[/tex]
[tex] \frac{2}{3} de30 \\ 30 \div 3 = 10 \\ 10 \times 2 = 20[/tex]
[tex] \frac{5}{8} de24 \\ 24 \div 8 = 3 \\ 3 \times 5 = 15[/tex]
[tex] \frac{7}{8} de56 \\ 56 \div 8 = 7 \\ 7 \times 7 = 49[/tex]
[tex] \frac{1}{3} de21 \\ 21 \div 3 = 7 \\ 7 \times 1 = 7[/tex]