<PRE><B>Question 1201805</B>
&lt;br&gt;
Find the value of 1-2+3-4+{{{cross(4)}}}5-6+...-100&lt;br&gt;
Presumably that is the expression you need to evaluate.  It doesn&#39;t take a lot of effort to look at what you are posting before you post it, to see it you are posting it correctly....&lt;br&gt;
1-2+3-4+5-6+...+99-100&lt;br&gt;
Group the terms in pairs:&lt;br&gt;
(1-2)+(3-4)+(5-6)+...+(99-100)&lt;br&gt;
(-1)+(-1)+(-1)+...+(-1)&lt;br&gt;
That&#39;s 50 pairs, each with a sum of -1, so the sum of all the numbers is 50(-1) = -50.&lt;br&gt;
ANSWER: -50&lt;br&gt;
</PRE>