Помогите пожалуйста, начиная с 11!! Алгебра 7 класс, пожалуйста!

$11)( \frac{10}{3} ) {}^{2} - ( \frac{9}{2} ) {}^{2} = \frac{100}{9} - \frac{81}{4} = \\ 11 \frac{1}{9} - 20 \frac{1}{4} = 11 \frac{4}{36} - 20 \frac{9}{36} =$
$= - 9 \frac{5}{36}$
$12) (\frac{31}{6} ) {}^{2} - ( \frac{22}{3} ) {}^{2} = \frac{961}{36} - \frac{484}{9} = \\ = 26 \frac{25}{36} - 53 \frac{7}{9} = 26 \frac{25}{36} - 53 \frac{28}{36}$
$= - 27 \frac{3}{36} = - 27 \frac{1}{12}$
$13)(51 - 41)(51 + 41) = \\ = 10 \times 92 = 920$
$14)(54 - 46)(54 + 46) = \\ 8 \times 100 = 800$
$15)(76 - 24)(76 + 24) = \\ = 52 \times 100 = 5200$
$16)(328 - 172)(328 + 172) = \\ 156 \times 500 = 78000$
$17)( \frac{11}{3} ) {}^{2} - ( \frac{7}{3} ) {}^{2} = \frac{121}{9} - \frac{49}{9} \\ 13 \frac{4}{9} - 5 \frac{4}{9} = 8$
$18) (\frac{68}{9} ) {}^{2} - ( \frac{40}{9} ) {}^{2} = ( \frac{68}{9} - \frac{40}{9} ) \times \\( \frac{68}{9} + \frac{40}{9}) = \frac{28}{9} \times \frac{108}{9} =$
,
$= \frac{28 \times 12}{9} = \frac{28 \times 4}{3} = \frac{112}{3} = 37 \frac{1}{3}$