https://whiterosemaths.com/homelearning/early-years/first-then-now-week-1/

Session 4 - Adding more- Unknown Then

Session 5 - Adding more - First Unknown

https://whiterosemaths.com/homelearning/early-years/first-then-now-week-2/

Session 1 - Taking away with pebbles

Session 2 - Taking away (1)