w children were riding on the bus. At the bus stop x children got on the bus while some got off the bus. Then there were y children altogether on the bus. How many more children got on the bus than those that got off?

There were w children riding on the bus to start. 

Then, x children got on the bus while some got off the bus. This means that the number of children on the bus increased by x. 

Now, there are y children altogether on the bus. 

To find out how many more children got on the bus than those that got off, we need to compare y to w. y is larger, which means that more children got on the bus than those that got off.