Answer :
The ratio here is 5:1 (bus kids to walkers). Because of this, we can assume that there are 6 total parts. 24/6 is 4. Therefore, one part is equal to 4. In the ratio, 5 parts of students take the bus (I know that sounds a bit strange but I hope you still follow) and 5*4 is 20. The remainder is 4 so four children walk and 20 take the bus. Because you want to see how MANY more take the bus, this shows that we must use subtraction. 20-4 is equal to 16 so that should be your answer. Let me know if you need me to clarify anything