How many monday thru fridays are in a year?

Without weekends, there are 260 or 261 days in a year (depends on whether it's leap year or not). There are 52.14 weeks in a year and two weekend days in each, so multiply 52.14 by 5 to get 261 (when rounded up).
Hope this helps :-)

It should be about 251 days that are from monday though friday

The reporter forgot to multiply the decimal by 100, making it 25%