The students are struggling with the models for subtraction. I have sent home a homework page with them today, please have students draw pictures and match up the groups and compare to help them get their answers.
For example: #1 Ashlee saw 8 lizards. Ian saw 5 lizards. How many more lizards did Ashlee see than Ian?
Students would draw a line to match the top group to the bottom group, compare the two groups and know Ashlee saw 3 more lizards than Ian.
Also here is a video link to help with the concept as well.