Ihave no clue what the answer to this is .

Arrange the numbers in order from smallest to largest:
12, 18 , 25, 26 , 30, 31 , 34

Find the highest and lowest numbers, those would be where the black dots go on the number line.

Lowest number = 12
 Highest number = 34

The line inside the box would be the Median number of the set.
Find the median (  middle value):
 Since there is an odd amount of numbers the median would be the middle number:
 Middle number = 26
 

The graph that has the black dots on 12 and 34 and the line of 26 is the first one