Even Numbers: let a1,a2,a3 are even => a1+a2 is even => closure property is satisfied a1+(a2+a3) = (a1+a2)+a3 => Associative a1 +0 = a1 => Identity element exists a1-a1 = 0 => inverse exists => even integers set is a group ODD Numbers let a1,a2 be two odd numbers => a1 +a2 is even => NOT closed => Odd integers is not a group Solution Even Numbers: let a1,a2,a3 are even => a1+a2 is even => closure property is satisfied a1+(a2+a3) = (a1+a2)+a3 => Associative a1 +0 = a1 => Identity element exists a1-a1 = 0 => inverse exists => even integers set is a group ODD Numbers let a1,a2 be two odd numbers => a1 +a2 is even => NOT closed => Odd integers is not a group.