Question 985294
The main formula we are going to use here is called the Closed Form. 

The sum from 1 to n is n(n+1)/2.

So Let's take the sum from 1 to 43 first.  That would be 43(44)/2 = 946.

Notice that in order to get the sum from 17 to 43, we need to subtract off 1 through 16.

So the sum from 1 to 16 is  16(17)/2 = 136

So 946 - 136 = {{{highlight(810)}}}