Give a number that is counter example to the conjecture below. Explain
your answer choice.
ALL NUMBERS THAT END IN THE DIGIT 3 ARE PRIME.

Hello.

Statement: ALL NUMBERS THAT END IN THE DIGIT 3 ARE PRIME.

Counter-example: 33

Explanation:
A prime number has only two factors, one and itself, so it cannot be
divided evenly by any other numbers. 33 ends in the digit 3, but 33 is
NOT prime. 33 may be divided evenly by integers other than 1 and 33.
Specifically, 33 may be divided evenly by 3 and 11.

More information on prime numbers from math.com:
http://www.math.com/school/subject1/lessons/S1U3L1DP.html

search strategy: "a prime number"

I hope this helps.