You can put this solution on YOUR website! This problem is a arithmetic progression:
n = 100 -- the number of entry
a1 = 2 (since even, so it will start with 2)--this our 1st element
d = 2 (the common difference), remember that the difference of the succeeding even is 2
S = n[ a1 + (n-1)d]/2
= 100[2 + (100-1)(2)]/2
S = 10,000