A={2,4,6,8,10} and b={1,2,3,4,5}
which solution set is the union a u b?
a. {2,4}
b.{1,2,3,4,5,6,8,10}
c.{1,3,5}
d.{7,9}

The union of the sets is the combination of all the elements of the sets with them listed only once. In the given above, A U B = (1, 2, 3, 4,  5, 6, 8, 10). The numbers 2 and 4 are repeated but we have to write them only once. The answer is letter B. 

52 or what they said ☝️