Remember: even±even/odd±odd = even & odd±even = odd
(or para mas madali, pag same=even at pag magkaiba=odd
1) p (even) + p (even) = even + n (odd) = odd
2) odd+odd = even + odd = odd + even = odd
3) 19-17 = 2 = even
4) 6+7+8+9 = 30 = even
Note: bold=given ; underlined=answer