Question 90866
all you have to do is find the factors and see which ones repeat.

112 = 2x2x2x2x7

28=2x2x7

And under a radical sign, you can take out the ones that repeat twice and put it in front. 

So therefore, 112 = 4 square root of 7, and 28 = 2 square root of 7.

Since both have square roots of seven, add them together and you get 6 square root of 7.

hope that helped :)