This problem could be set up algebraically or you could use trial and error.
a) 9 and 4 (9 + 4 = 13, 9 * 4 = 36 and 36 - 23 = 13)
I won't give you the rest of the answers, but the second and third ones have to add together to equal a negative number and multiply to equal a positive number. I hope this helps some.