To solve the problem, set up a proportion like this:

The important thing to note here is that the fractions are proportionate to one another. Meg's cat is in the numerator while Anne's cat is in the denominator. Use cross multiplication to solve for the weight of Anne's cat.

Anne's cat weighs 28 kgs. The question asked how much
more her cat weighs than Meg's, so use subtraction:
28 - 20 = 8
Anne's cat weighs 8 kgs more than Meg's cat.