S14
I can subtract HTU - HTU with exchanging.
S15
I can subtract £ and p.
S16
I can subtract ThHTU – HTU.
S17
I can subtract U.t – U.t.
S18
I can subtract numbers with different amounts of digits.
S19
I can subtract U.th – U.th.
S20
I can subtract whole numbers and decimals.
S21
I can subtract negative numbers in a context (e.g. temperature).