Answer:
You can build 3,240 different home theater systems.
Explanation:
The possible combinations can be calculated multypling the number of TVs available, the number of sorround systems available and the amount of DVD players avalaible.
This is because for each type of TV, we can combine it with any type of sorruond system. This makes 15 combinations for each TV type. If we have 9 TV types, we have 9*15=135 combinations. Each of these combinations can be completed with one of the 24 types of DVD player, so we have 135*24=3240.