Me . i don't understand this section

What you do is that you use your algebraic magic to find your c value. First, you will divide both sides by 5. Now you have 2b= the square root of c +2. Now subtract 2 from both sides and you will have 2b-2= the square root of c. To undo the square root of c, you will need to square it, so square both sides and you have your answer. Good luck!

The answer should be 3%