Question

Proposed proof: Suppose that n or m are even. Then n = 2k and m = 2j for some integers k and j. This shows that n*m = (2k)*(2j) = 4k*j. Therefore, n*m is even

Answer 1

Suppose that m is even and n is odd.
So, m=2k,n=2i+1.
Thus, mn=2k(2i+1)=2l is even.