To solve the equation \(-1.2 = x + 5.1\), you can isolate \(x\) by subtracting \(5.1\) from both sides of the equation:
\[ -1.2 - 5.1 = x \]
Now, calculate the left-hand side:
\[ -1.2 - 5.1 = -6.3 \]
So, the solution for \(x\) is:
\[ x = -6.3 \]