"How to add fractions with different denominators." I've found this helpful for students for whom this is visually overwhelming, and it extends well into subtraction.
I did that when to my *amazement* after I sent an email to Camtasia explaining how my old version had been deleted from work computer... and no, I didn't expect itto happen today, but how could I get it back? Almost instantly... I got my purchase code and a link to download.
I'd just finished this on Screen-Cast-O-Matic https://www.youtube.com/watch?v=QykNdW3TIr0&t=9s about finding common denominator with times tables chart.
I need to figure out some details such as having it include the link to captions without having to start the video, and oh, some links on the page to go someplace useful so the 'back' button isn't necessary... so I'll probably put it up on YouTube too...