Solving more maths problems

This task is about solving some maths problems.
illustration: train
 
a) There are 28 people at a picnic, and 12 people leave. Show how to work out how many people stay at the picnic.
 
 
 
 
 
 
 
Answer: __________  
 
b) A train has 65 people on board, and 27 get off. Show how to work out how many people stay on the train.
 
 
 
 
 
 
 
Answer: __________  
 
c) Devon has 85 flowers to make lei.  She gives 39 of them to her friend. Show how to work out how many flowers she still has.
 
 
 
 
 
 
 
Answer: __________