There’s no answer choices..
I'm assuming there is probably a graph that goes with this problem so here is all the info I can give you with the four choices:
If it is -1/3, the line will go DOWN 1, over 3 (just count on the graph)
If it is 3, the line will go UP 3, over 1
If it is 1/3, the line will go UP 1, over 3
And if it it -3, it will go DOWN 3, over 1
(If the slope is 3 or -3, it would be quite steep compared to a slope of 1/3 or -1/3)
Hope that helps!
Answer:

Step-by-step explanation:
Given:

1.

2.

3.

4.

5.

6.

7.

8.

Euler's formula is given by:
C + V = A + 2
Where,
C: number of faces
V: number of vertices
A: number of edges.
Clearing A we have:
A = C + V-2
Substituting values:
A = 21 + 14-2
A = 33
Answer:
the missing number is:
C.33