I believe that the answer to your question can be defined in a few simple steps.
1) First, you are trying to find out how many red chairs there are, therefore, we will label the red chairs as "x"
2) Second, they are telling you that there are "17 more than twice the number of red ones" . This means that the equation would be 17+2x+x=50. seventeen more (+) blue chairs than twice (2x) the number of red ones (x), and this would all equal 50, because that is the total of chairs that you are given. S
3) Lastly, solve for x and you should come up with x=11
So you have 11 red chairs. You can check your work by plugging in the number into the formula
Hope this helped!