You have 4 marbles and you can get 3 combinaisons of two marbles for each one.
So 4*3 = 12.
There are 12 outcomes. The answer would be D.
Hope this helps !
Photon
19-13p=-17p-5
+5 +5
24-13p=-17p
+13p +13p
24=-4p
/-4 /-4
-6=p
The answer is A. (2,2)
so basically what i did was 16-(-12)=28 and then divide 28 by 2 which is 14 and i went 14 points positive from -12 to find the midpoint, which is 2.