Posted by Sue on Monday, February 4, 2008 at 1:58pm.
Wich if the given numbers are composite?15,19,23,31,49,55,59,87,91,97,103,105

math  drwls, Monday, February 4, 2008 at 2:10pm
Compare to the list of them here:
http://www.mathworksheets.info/Composite_numbers.html
The list goes as far as 100. Beyond that, 103 is prime and 105 has more than two prime factors (5,21,3,35,7, and 15), so they are not composite.