Question

a class voted for either kayaking, fishing, or hiking as their favorite summer activity. if hiking got 17% percent of the vote and fishing got 33%, what percentage of the class voted kayaking?

Answer 1

50%
100-17-33
Just the difference after subtraction<span />

Answer 2

In a problem such as this one, the percentages have to add up to 100%.
Thus, if you have 17% and 33% already, and add them together, you get 50%.  Subtracting 50% from 100%, you obtain 50%.  So:  50% of the class voted kayaking.