Answer:
We conclude that the first line number represents 1.5 + 2.5.
Explanation:
Given the expression

It means the first segment must represent 1.5 units starting from 0.
Since we have to add 2.5 to 1.5, so the next segment must represent 2.5 units, starting from 1.5
Combining them would make

Now, if we observe the first number line,
- The first arrow represents the 1.5 units starting from 0.
- The second arrow represents the 2.5 units starting from 1.5.
- The combined units of both arrows represent the length of 4 units. i.e. 1.5 + 2.5 = 4
Thus, we conclude that the first line number represents 1.5 + 2.5.
The correct line number is also attached below.