b#~8=+/"1 sep b=.a#~54=|a-10#.|."1 sep a=.10 to 99
17 71
Alternately:
10#.b#~(8=+/"1 b)*.54=|a-10#.|."1 b=.sep a=. 10 to 99
The answer is 71.
71 - 17 = 54.
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