there are currently 3 students signed up for a trip. the van can transport only 7 students.  which graph shows all the possible values for the extra number of students that need to sign up so that more than one van is needed to transport them?          

Number line with open circle on 4 and shading to the right.

Solution:

Call x the number of students that need to sign up so that more than one van is neeed to transport them, then:
 
x + 3 > 7

=> x > 7 - 3

=> x > 4

That is the numbers greater than 4, without including the number 4.

That, in the number line, is the set of numbers to the right of 4, and the open circle is used to indicate that the number 4 is not included (a closed circle would indicate that the number 4 is included, which is not the case).