The segment of the number line between 3 and 33 has length $33 - 3 = 30$. Since this segment is divided into six equal parts, then each part has length $30 \div 6 = 5$. The segment $PS$ is made up of 3 of these equal parts, and so has length $3 \times 5 = 15$. The segment $TV$ is made up of 2 of these equal parts, and so has length $2 \times 5 = 10$. Thus, the sum of the lengths of $PS$ and $TV$ is $15 + 10$ or 25.