Algebra

To complete this problem, we must make an important observation.

NOTE: 

$3 + 4 + 5 = 3 *4 \\ 13 + 14 + 15 = 3 * 14$

Now, we just have to figure out $3 [ 4 + 14 + 24 + ....... + 994 ] =$

There are 100 terms in the sequence, so we have

$3 [ 994 + 4 ] [ 100 / 2 ] = 149,700$. 

Thanks! :)