Question 305325
Not sure who wrote this problem, but if it is written EXACTLY as you show, then 
100%  

There are only two colors in there, so "what is probability that it is black or white"?? The key here is the word "or". Logically, "black or white" means that as long as the ball is either white or black, then the logical outcome is "true". Since there are ONLY black and white balls in the urn, the answer is 100%

I am betting the book or the teacher won't like your answer -- but it IS correct.