The lampposts are the number 15, the snowmen are the number 4, and the trees are the number 3. Then in the last equation, a light post with only one light would represent the number 5. If you go by the order of operations, 3 multiplied by 4 is 12, then if you add 15 and subtract 5 you’ll get 22.
Are you a numbers nerd? Laugh along at 36 maths jokes.