1. The problem is to subtract two decimal numbers: $3.428 - 5.42$. 2. To subtract, align the decimal points: $$\begin{array}{r} 3.428 \\ -5.420 \\ \hline \end{array}$$ 3. Since $3.428$ is smaller than $5.42$, the result will be negative. 4. Subtract $5.420 - 3.428$: $$\begin{array}{r} 5.420 \\ -3.428 \\ \hline 1.992 \\ \end{array}$$ 5. Therefore, the answer is: $$3.428 - 5.42 = -1.992$$ 6. So, the final result is $-1.992$.