Two angles in a triangle add up to 98 degrees . what is the size of the third angle ?

First you must know that the sum of the interior angles of a triangle are 180.  Once you know that, you just simply add 98+x=180 (you can use an variable as you see fit, doesn't need to be x). And then you simply solve for x by dividing 98 on both sides leaving you with 82.

The operation is suck a c@ck? !