First, take off the brackets. You have to

4x+ 16-x2=26

Then move the term, move the constant term 16, and get

4x-2x=26- 16

Merge similar items again and add and subtract in the same way to get

2x= 10

Finally, divide the two sides by the first coefficient of 2, and you get

x=5

So the answer is 5.

Ok, class is over.