Помогите решить... (4-2.5*3\5):3 1\3-1\3 16,8\21=X\35 X:12=X\36

$(4 - 2.5 \times \frac{3}{5} ) \div 3 \frac{1}{3} - \frac{1}{3} = (4 - \frac{25 \times 3}{10 \times 5} ) \div \frac{10}{3} - \frac{1}{3} = 4 \times \frac{3}{10} - \frac{3}{2} \times \frac{3}{10} - \frac{1}{3} = \frac{6}{5} - \frac{9}{20} - \frac{1}{3} = 1 \frac{1}{5} - \frac{9}{20} - \frac{1}{3} = 1 \frac{4 - 9}{20} - \frac{1}{3} = 1 - \frac{5}{20} - \frac{1}{3} = 1 - \frac{1}{4} - \frac{1}{3} = \frac{3}{4} - \frac{1}{3} = \frac{9 - 4}{12} = \frac{5}{12}$
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$\frac{16.8}{21} = \frac{x}{35} \\ 21x = 16.8 \times 35 \\ 21x = 588 \\ x = 588 \div 21 \\ x = 28$
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$x \div 12 = \frac{x}{36} \\ 36x = 12x \: \: \: | \div 12 \\ x = 3x \\ 3x - x = 0 \\ 2x = 0 \\ x = 0$