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).