Matching Pairs Subtraction MemoryOnline version Subtraction Memory by Nicholas Redmond 1 14-4 2 12-9 3 10-1 4 11-7 5 11-9 6 17-9 7 15-10 8 13-7 9 16-15 10 19-12 4 8 9 3 2 5 10 7 6 1