natural number: are those numbers that we use to count things: {1, 2, 3, 4, ...}
rational numbers: are those numbers that can be represented as a division between two integers, so in this case because we have a fraction it is a rational number.
whole numbers: are the natural numbers also including zero and negatives {...,-2,-1,0,1,2,3,---}
in conclusion 15/28 is a rational number because it is expressed as a division and it is not a whole or natural number
