1. The problem asks for the value of $x_4(3)$ from the training set. 2. Here, $x_4$ represents the "Age of home in years". 3. The subscript 3 indicates the third row in the data. 4. Looking at the third row under the "Age of home in years" column, the value is 30. 5. Therefore, $x_4(3) = 30$. Final answer: 30