whatever% of anything is just (whatever/100) * anything.
so we know the dog has a speed 150% that of the squirrel, and we know the squirrel can do 12 mph, what's 150% of 12? well is just (150/100) * 12, namely 18, so the dog can run 18 mph.
we know the cheetah is 310% the speed of a dog, and we know the dog can do 18 mph, what's 310% of 18? well, is just (310/100) * 18, namely 55.8.