Nursery rhymes are so important for many reasons but a great nursery rhyme that encourages early counting and subtracting skills is Five Little Ducks.
Here is the link to the song- https://www.youtube.com/watch?v=pZw9veQ76fo&feature=youtu.be
And an activity idea to make your very own duck pond which would support your little ones with re-telling the rhyme and their counting -https://www.messylittlemonster.com/2015/06/five-little-ducks-egg-carton-craft.html?m=1