Помогите пожалуйста разобраться в этих пропорциях

▪3)

$\frac{2.7}{9} = \frac{1 \frac{1}{5} }{3x + 1} \\ 2.7(3x + 1) = 9 \times 1 \frac{1}{5} \\ 2.7(3x + 1) = \frac{9 \times 6}{5} \\ 2.7(3x + 1) = \frac{54}{5} \: \: \: \: \: | \div 2.7 \\ 3x + 1 = \frac{54 \times 10}{5 \times 27} \\ 3x + 1 = 2 \times 2 \\ 3x = 4 - 1 \\ 3x = 3 \: \: \: \: \: | \div 3 \\ x = 1$

▪4)

$\frac{1 \frac{4}{5} }{2.5} = \frac{7.2}{6x + 1} \\ 6x + 1 = \frac{2.5 \times 7.2}{1 \frac{4}{5} } \\ 6x + 1 = \frac{18}{ \frac{9}{5} } \\ 6x + 1 = \frac{18 \times 5}{9} \\ 6x = 2 \times 5 - 1 \\ 6x = 9 \\ x = \frac{9}{6} = \frac{3}{2} = 1 \frac{1}{2} = 1.5$

▪5)

$\frac{6}{1 \frac{4}{5} } = \frac{3x + 0.6}{2.88} \\ 3x + 0.6 = \frac{6 \times 2.88}{1 \frac{4}{5} } \\ 3x + 0.6 = \frac{17.28}{ \frac{9}{5} } \\ 3x + 0.6 = \frac{17.28 \times 5}{9} \\ 3x = 9.6 - 0.6 \\ x = 9 \div 3 \\ x= 3$

▪6)

$\frac{ \frac{3}{8} }{0.75} = \frac{0.6}{x - 2.8} \\ \frac{3}{8} (x - 2.8) = 0.75 \times 0.6 \\ \frac{3}{8} (x - 2.8) =0.45 \: \: \: \: \: | \div \frac{3}{8} \\ x - 2.8 = \frac{45 \times 8}{100 \times 3} \\ x - 2.8 = \frac{15 \times 2}{25} \\ x = \frac{6}{5} + 2.8 = 1 \frac{1}{5} + 2.8 = 1.2 + 2.8 = 4$