Rational numbers can be expressed as the ratio between to integers, p or q and can be expressed as p/q, an example of a rational number could be:
As it has two integers and its value its expressed with them, you can convert any number to a rational number by making a fraction where you divide it by 1.
The easiest way to do this is to plot the points. I used the pythagorean theorem for this one, too. Add the side lengths to get the perimeter: 5 + 5 + 5 + 3 + √40 = 24.32455532 units or just 24 units.