11, 13, and 16. sorry if im wrong, and i hope this helps.
4,6,8 are being counted by twos so the next one is 10
4•3= 12, 6+3=9, 8-3=6, the next operation I assume would be division so 10/3= 3.34
(-8 + 0 / 2) (7 + 1 / 2)
(-8/2) (8/2)
(-4) (4)
Midpoint = (-4,4) [Answer]
Solution :
Let A = Economics, B = Mathematics
n(A) = 311, n(B) = 243, 
a). So, 
= 311 + 243 - 135
= 419
b). n(A only) = 311 - 135
= 176
n(B only) = 243 - 135
= 108
Exactly one of these two courses

= 0.568
c). Neither economics nor mathematics


= 0.162