Question 138930
Use Venn Diagrams:
Draw two overlapping circles
Let the intersection be 65%
Then the rest of the mustard circle is 15%
and the rest of the ketchup circle is 10%
Adding 65+15+10 you get 90%
That leaves 10% that do not use ketchup or mustard.
So 90% use mustarard, ketchup or both.
Cheers,
Stan H.