Is -15 a whole number, integer, or a rational?

Integer and rational

Explanation:

The set of whole numbers is defined to be {0, 1, 2, 3, } so it's composed of numbers that don't have any decimal or fractional components. We start at 0 with this set. We don't include negative numbers here.

Integers are basically the same as whole numbers, but now we include negative values {..., -3, -2, -1, 0, 1, 2, 3, ...} so we see that -15 is in the set of integers.

The value -15 is also a rational number because -15 = -15/1, meaning we can write -15 as a fraction of integers. Any rational number is of the form a/b with a,b being integers and b is nonzero.