How do we find the measure for this problem

In a triangle, there should be 180 degrees total. Since the measure of one angle has already been found (98 degrees), subtract that amount from 180 so you know what the other two angles should be when added together:
180-98=82

The missing angles are both equal to x, so they should be the same measure. Simply divide 82 by 2 to get 41 degrees.
The measures of the missing two angles are 41 degrees and 41 degrees.

If this is an isosceles triangle...
it should equal to 180
so 180 = 98 + 2x
subtract 98 from both sides this will equal 82
now 82 = 2x
divide both sides by 2 to isolate the variable
x = 41
this means that IF IT IS AN ISOSCELES TRIANGLE both angles E and F equal 41 degrees.

Hope this helps ;)