Answer:
This is the even numbers out of 100. So Do every other one so in you case 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30.And all them problem you do add up to 15 total of what you completed( why they said there will only be 15 problems AKA the ones you solve)
Explanation:
Hope this helps :)