The Butcher's algebraic formula & The Bellman rings his bell

The Butcher's algebraic formula, an illustration by JVL in Lewis Carroll's 

The Hunting of the Snark, Artists' Choice Editions, 2006.

The Text:

 90

So engrossed was the Butcher, he heeded them not,

 As he wrote with a pen in each hand,

 And explained all the while in a popular style

 Which the Beaver could well understand.

 91

"Taking Three as the subject to reason about--

 A convenient number to state--

 We add Seven, and Ten, and then multiply out

 By One Thousand diminished by Eight.

 92

"The result we proceed to divide, as you see,

 By Nine Hundred and Ninety Two:

 Then subtract Seventeen, and the answer must be

 Exactly and perfectly true.

 93

"The method employed I would gladly explain,

 While I have it so clear in my head,

 If I had but the time and you had but the brain--

 But much yet remains to be said.

The Bellman rings his bell, an illustration by JVL in Lewis Carroll's 

The Hunting of the Snark, Artists' Choice Editions, 2006.