To solve the equation \(-1.2 = x + 5.1\), you need to isolate \(x\). Here's how you can do that:
- Subtract \(5.1\) from both sides of the equation:
\[ -1.2 - 5.1 = x \]
- Perform the calculation on the left side:
\[ -6.3 = x \]
So, the solution is:
\[ x = -6.3 \]