U = {x ∈ Z | 0 ≤ x ≤ 20} = {0,1,2,3,...,20};

A = set of all even integers = ;

B= set of all prime numbers = ;

C = set of all numbers coprime with 2 = ;

{y ∈ U | y= 2z + 3, for some z∈Z} 

To do the last one:



Solve for z in the middle.
Subtract 3 from all three sides:



Divide all three sides by 2



Since z is an integer,

 = {-1,0,1,2,3,...,8}, substitute each 
in 2z+3:

{y ∈ U | y = 2z + 3, for some z ∈ Z} = {1,3,5,7,...,19}

Edwin