Every step a dog walks is 1 foot. Every 4 steps a dog walks is the same as 5 steps of a cat. So the distance covered by 4 steps of a dog is 4 feet. So now we know that the distance a cat walks 5 steps is 4 feet.

So they want to know how how far a cat walks in 20 steps. So we want to find how many groups of 5 steps are there in 20 steps. Thus we use 20/5 = 4 groups of 5 steps.

1 group of 5 steps = 4 feet
4 groups of 5 steps = 4 x 4 = 16 feet