Whole number are actual counting number except for zero. Example of whole numbers are 1, 2, 3, 4, 5, 6, 7, 8, 9. Generally, whole numbers don't have fraction.
Integers are similar to whole number with no fractions but negative numbers are also included examples include - 5, -4. -3, -2, -1, 0, 1, 2, 3, 4, 5
Rational numbers are formed by dividing 2 integers. Rational number can be represented as x/y where y is not = 0. The decimal of rational number have an end . example of rational numbers are -3/2, - 6.75, 1/2 etc
Natural numbers are number we can count .
Therefore the number - 6.75 is best regarded as a Rational number . -6.75 can be represented as 27/4.