Remember BIDMAS or PEMDAS
Focus on the parentheses first.
(5 + 6 - 6) is 5
Rewrite the equation.
5 + 5 + 3 + 3 - 2
Add.
16 - 2
Subtract.
14
3 + 6 + 9 + 12 + ... + 999
<span>= 3(1 + 2 + 3 + 4 + ... + 333) </span>
<span>= 3(Summation of r from 1 to 333) </span>
<span>= 3((1 + 333)(333/2)) </span>
<span>= 3(334)(333/2) </span>
<span>= 3(167)(333) </span>
<span>= 166833 </span>
<span>Edit: Opps, I forgot that you ask about an equation. </span>
<span>The sum of 1 + 2 + 3 + 4 + ... + n, where n is some integer, is: </span>
<span>(First term + Last term) multiplied by (Total number of terms / 2) </span>
<span>= (1 + n)(n / 2)</span>
Eighty million, forty thousand, nine hundred sixty.