During the course of a year, the price of a house increased from $200,000,000 to $250,000. what was the percent increase in price?

 The equation for percent increase is: (x-y)/y, where x is the final price and y is the beginning price. 
So for this problem we substitute to get: 
(250000-200000) / 200000 
We subtract the 200000 to get: 
50000 / 200000 
We divide by 200000 to get: .25  
We can convert this to percent by multiplying by 100. We get: 25%
Hope this helps.