Some tricky questions that arise in class and in homework are:
What number is 5 less than 9? or What number is 12 less than 20. These are tricky because students automatically want to do 5 - 9 and 12 - 20. At home you can practise these questions with sultanas. Ask a similar question while eating the sultanas, to find out how many sultanas left.
We have also been practising drawing number lines that do not start at 0. For example for the question 30-5. One where the lines starts at 30 and they count back 5. Feel welcome to try one of these at home to explore the concept further with your child.