Помогите пожалуйста со всеми номерами, дам 20б

$1)18 \times \frac{1}{81} - 20 \times \frac{1}{9} = - 2 \\ 18 \times \frac{1}{81} = \frac{6}{27}$
$20 \times \frac{1}{9} = \frac{20}{9} = 2 \frac{2}{9}$
$\frac{6}{27} - 2 \frac{2}{9} = \frac{6}{27} - 2 \frac{6}{27} = - 2$
2)
$\frac{4}{25} + 3 \frac{3}{4} = \frac{16}{100} + 3 \frac{75}{100} = 3 \frac{91}{100}$
3)
$1 \frac{1}{2} - 1 \frac{4}{5} = 1 \frac{5}{10} - 1 \frac{8}{10} = - \frac{3}{10} = \\ = - 0.3$
4)
$4)2 \frac{3}{8} + \frac{11}{12} = 2 \frac{9}{24} + \frac{22}{24} = 2 \frac{31}{24} = \\ = 3 \frac{7}{24}$
$3 \frac{7}{24} \div \frac{5}{48} = \frac{79}{24} \times \frac{48}{5} = \\ \frac{79 \times 2}{5} = \frac{158}{5} = 31.6$
5)
$\frac{12}{20 \times 3} = \frac{1}{5}$
6)