If you have more than four photos to hand in, here are some suggestions.
UPDATE: see Multiple Uploads
Firstly, please ask if it is really necessary to upload more than four photographs. We do not need to see work from a lesson where the answers were provided on the next page.
Hand in the first photo with the 2Do. Then make a folder in your My Work (for example, make a Maths folder) and then upload the remaining files there. You need to tell your teacher that you’ve done so because they do not get a notification. Tell them in the 2Do comment or send them a 2Email.
There are lots of smartphone apps that combine several photos into a single PDF. You may already have a favourite that you use for receipts and expenses. Use one that lets you adjust the size of the resulting PDF. It must be under 16MB in order to upload. Be careful when choosing apps. Check that they only request permissions to your photos and that it is easy to avoid in-app purchases.
There are also ways to do it after transferring the photos to your computer. To keep below the 16Mb limit, you will need to reduce the size of the photos first.