11487 − 10 = working
12523, counting back in hundreds: , , , working
13 = 596 + 10working
14253 − 10 = working
151000, counting back in ones: , , , working
16 = 873 − 100working
17103, counting back in ones: , , , working
18542 − 100 = working
19 = 601 − 10working
20203 − 10 = working