The total number of snowstorms is 60.
If 65% caused power outages, then the 21 storms that didn't represent 35% because 65%+35%=100%. You can set up a proportion (35/100=21/?) and use cross multiplication to find the total number of snowstorms. So, 21x100=2,100 and then 2,100 divided by 35 is 60.