Have a go at budgeting for your Christmas party. You could consider the amount of people you are spending dinner with and look in the shops/ online shopping/ in a catalogue for how much money items for Christmas dinner cost. How much will your dinner cost in total? Can you write a menu which stays under £50?
There is a sheet below you could use for this task.
Medium: Try adding and subtracting to 20. Here's a Christmassy sheet you can do if you choose.