Here the 1907 LDS vest-pocket edition accidentally omitted the repeated definite article the from the conjoined noun phrase “the cunning and the craftiness of king Laman”. This edition was not used as a copy-text for any subsequent edition; thus the correct reading has been maintained in the LDS text. Of course, this tendency to omit the repeated determiner is common in the history of the text. For a list of examples, see the discussion in volume 3 under conjunctive repetition.
There are two other instances of conjoined cunning and craftiness in the text, both of which refer to king Laman:
In these two instances, the determiner (either the or his) is not repeated for the second conjunct craftiness, although in Mosiah 10:18 the his is repeated for a third conjunct (“and his fair promises”). But Mosiah 9:10 shows that in the original text the determiner can be repeated when cunning and craftiness are conjoined. Since variation is possible, we follow the earliest textual sources for each instance of this conjunctive noun phrase.
Summary: Maintain the repeated the in Mosiah 9:10: “the cunning and the craftiness of king Laman”.