Final answer:
A counterexample to the claim that if a number is divisible by 4, it is also divisible by 8 is the number 12, which is divisible by 4 but not by 8.
Step-by-step explanation:
To counter Wilma's claim that if a number is divisible by 4, then it is also divisible by 8, we need to find a number that disproves this statement. Essentially, we need to find a number that is divisible by 4 but not divisible by 8. An example of such a number is 12. When we divide 12 by 4, we get 3, which means 12 is divisible by 4. However, when we try to divide 12 by 8, we do not get a whole number, showing that 12 is not divisible by 8. This clearly demonstrates that not all numbers divisible by 4 are also divisible by 8, and so, the number 12 serves as a counterexample to Wilma's claim.