Repunctuate the following sentence in the structural style.

The strange boy whistled; and put his hand into his pocket, as far as the big coat sleeves would let them go.

The correct way to repunctuate the sentence in the structural style is the following one:

The strange boy whistled and put his hand into his pocket as far as the big coat sleeves would let them go.

Explanation:

"The strange boy whistled and put his hand into his pocket" is a quick sequence of actions, and as so it needs no pause, that is, no comma, let alone a semicolon.

"as far as the big coat sleeves would let them go" is an adverb clause, and adverb clauses that appear at the end of a sentence do not have to be preceded by a comma.

The strange boy whistled and put his hand into his pocket, as far as the big coat sleeves would let them go.

Semicolon is not correct before the conjunction "and".