Answer:
 = {1,3,5,7,9,....}
 = {1,3,5,7,9,....}
 = {1,2,4,5,7,8,10,11,13,14......}
 = {1,2,4,5,7,8,10,11,13,14......}
 = {1,2,3,4,5}
 = {1,2,3,4,5}
 = {10,11,12,13,14,15,......}
 = {10,11,12,13,14,15,......}
Step-by-step explanation:
Solution: 
It is given that, Universal set is the set of all Natural Numbers.
and 
Set A, Set B, Set  C, Set D are subsets of Universal set. 
A = {x:x is even natural numbers} = {2,4,6,8,10,.....}
B = {x:x ∈ N and x is a multiple of 3} = {3,6,9,12,15,....}
C = {x:x∈ N and x < 5} = {6,7,8,9,10,.....}
D = {x:x ∈ N and x > 10} = {1,2,3,4,5,6,7,8,9}
U = {1,2,3,4,5,6,7,8,9,10,11,........}
Complements:
 = U-A = {1,2,3,4,5,6,7,8,9,10,11,........} - {2,4,6,8,10,.....}
 = U-A = {1,2,3,4,5,6,7,8,9,10,11,........} - {2,4,6,8,10,.....} 
 = {1,3,5,7,9,....}
 = {1,3,5,7,9,....}
 = U-B =  {1,2,3,4,5,6,7,8,9,10,11,........} - {3,6,9,12,15,....}
 = U-B =  {1,2,3,4,5,6,7,8,9,10,11,........} - {3,6,9,12,15,....}
 = {1,2,4,5,7,8,10,11,13,14......}
 = {1,2,4,5,7,8,10,11,13,14......}
 = U-C = {1,2,3,4,5,6,7,8,9,10,11,........} - {6,7,8,9,10,.....}
 = U-C = {1,2,3,4,5,6,7,8,9,10,11,........} - {6,7,8,9,10,.....}
 = {1,2,3,4,5}
 = {1,2,3,4,5}
 = {1,2,3,4,5,6,7,8,9,10,11,........} - {1,2,3,4,5,6,7,8,9}
 = {1,2,3,4,5,6,7,8,9,10,11,........} - {1,2,3,4,5,6,7,8,9}
 = {10,11,12,13,14,15,......}
 = {10,11,12,13,14,15,......}