Ответ:

[tex]x = 0.3[/tex]

Пошаговое объяснение:

[tex]3(3.6x + 4.2) + 3.2x = 16.8 \\ 10.8x + 12.6 + 3.2x = 16.8 \\ 14x + 12.6 = 16.8 \\ 14x = 16.8 - 12.6 \\ 14x = 4.2 \\ x = 4.2 \div 14 \\ x = 0.3[/tex]