1. The problem is to find the result of the subtraction $22.4 - 19.29$. 2. The formula for subtraction is $a - b = c$, where $a$ and $b$ are numbers and $c$ is the difference. 3. Align the decimal points and subtract: $$\begin{array}{r} 22.40 \\ -19.29 \\ \hline \end{array}$$ 4. Subtract digit by digit from right to left: $$\begin{array}{r} 22.40 \\ -19.29 \\ \hline 3.11 \\ \end{array}$$ 5. So, $22.4 - 19.29 = 3.11$. The answer is $3.11$.