Let's break down the problem step by step:

• You have a bedroom wall that is 15 feet wide.
• There are three posters to hang, and each poster is 2 feet wide.
• You want 3 feet of space between each end of the wall and the first/last poster.

Goal: Find out how much space is needed between the posters.

Step-by-step calculation:

1. Total width of the wall = 15 feet.
2. Width of the two end spaces = 3 feet each, so $3 \text{ ft} + 3 \text{ ft} = 6 \text{ ft}$.
3. Total width of the three posters = $3 \times 2 \text{ ft} = 6 \text{ ft}$.
4. Remaining space for gaps between posters: $\text{Remaining space} = 15 \text{ ft} - 6 \text{ ft (end spaces)} - 6 \text{ ft (poster widths)} = 3 \text{ ft}.$
5. Since there are two gaps between the three posters, the space between the posters is: $\text{Space between posters} = \frac{3 \text{ ft}}{2} = 1.5 \text{ ft}.$

Final Answer: You will need 1.5 feet of space between the posters.

Would you like more details or have any other questions?

Here are 5 related questions to expand on this:

1. How would the space between posters change if the posters were larger?
2. What if you wanted 4 posters instead of 3? How would you find the new gap size?
3. How would this change if the wall were 20 feet wide?
4. If the gap between posters were fixed at 2 feet, how would you determine the wall size required?
5. What if the posters were different sizes? How would you adjust the spacing?

Tip: When calculating spacing, always account for the fixed spaces (like wall edges or gaps) before distributing the remaining space evenly.