Here is an idea for you. In SMARTBoard these shapes have links to video clips. The idea is to order the video clips into the correct sequence. The video clips are steps to subtracting two mixed fractions together. Now you will want your class to order them. Here is how you can do that. Have pairs of students come up to the smartboard and click on a shape. Once they have watched the video clip the pair, as well as the rest of the class will discuss with each other where that video clip belongs in the sequence of the others. Maybe they will put it in the second place slot. Have them justify why they put it there. Have another pair of students come up and click on a different shape. They will watch the video clip. They then discuss with each other, as the rest of the class is discussing, where that clip belongs. This happens for as many steps or video clips you have. I think this really teaches a good example of how to do the problem, but more important it cements the order in which it is done. I have put the four videos that I made for this example in this post. I have also given instructions on how to do this with SMARTBoard Notebook software in a video below.