Ooh! A radical! Ok, so you have a quantity here of 4 • sqrt(5), correct? Now, to get this to one radical, obviously something needs to be done to the 4, as it is the only part of the quantity that isn't under the radical. So, we need to change it to where it'll be the same number value, just in a different form (i. e., we need to make it a radical). So what number, what put under the radical sign, makes 4? I'm hoping you're thinking 16. If not, then realize sqrt(16)=4. Now, we have the quantity sqrt(16)•sqrt(5). All that's left is to multiply 16 & 5 and make it one, "unsimplified" radical. Hope this helps!