For starters, you need to add 17 and 26 together, which equals 43. Then, you have to divide 43 by 2 because one man and one woman are going to be in each pair. 43 divided by 2 equals 21.5. you need to round 21.5 to the nearest one, and that would be 22.
So the number of pairs that could be chosen are 22. I hope I was able to solve your problem.