Final answer:
The set of numbers that contains -3 but not 0.333... is the set of integers.
Step-by-step explanation:
The set of numbers that contains -3 but not 0.333... is the set of integers. Integers include all positive and negative whole numbers, as well as zero.
Examples of numbers in this set would be -5, -3, -1, 0, 1, 5, etc. However, the number 0.333... is not an integer because it is a repeating decimal and cannot be expressed as a whole number.
Therefore, the set of numbers that contains -3 but not 0.333... is the set of integers.