30. x+1,2 / 2,4 = 6,8 / 3,6

Решение:

1. \[ \frac{x+1,2}{2,4} = \frac{6,8}{3,6} \]
2. \[ 3,6(x+1,2) = 2,4 \times 6,8 \]
3. \[ 3,6x + 4,32 = 16,32 \]
4. \[ 3,6x = 16,32 - 4,32 \]
5. \[ 3,6x = 12 \]
6. \[ x = \frac{12}{3,6} \]
7. \[ x = \frac{120}{36} \]
8. \[ x = \frac{10}{3} \]

Ответ: x = 10/3