-2,8*(3x+7)-4,2=1,4

To solve the equation \(-2.8(3x + 7) - 4.2 = 1.4\), follow these steps:

1. Distribute \(-2.8\) within the parentheses: \[ -2.8 \cdot 3x - 2.8 \cdot 7 - 4.2 = 1.4 \] This simplifies to: \[ -8.4x - 19.6 - 4.2 = 1.4 \]

2. Combine the constants on the left side: \[ -8.4x - 23.8 = 1.4 \]

3. Add \(23.8\) to both sides: \[ -8.4x = 1.4 + 23.8 \] This gives: \[ -8.4x = 25.2 \]

4. Divide both sides by \(-8.4\): \[ x = \frac{25.2}{-8.4} \]

5. Calculate the right side: \[ x = -3 \]

So, the solution is: \[ \boxed{-3} \]