任せる: leaving the menu or a repair to someone
Compare deciding to leave the dinner menu to the mother with entrusting a difficult repair to an artisan. Identify the delegated task and person without extending the menu decision to all household work.
Deciding to leave the dinner menu to the mother
「夕食の献立は母に任せることにした。」 (I decided to leave the dinner menu to my mother.)
The decision concerns the dinner menu. It does not transfer every part of preparing the meal, or every other household task, to the mother.
Entrusting a difficult repair to an artisan
「難しい修理を経験豊かな職人に任せた。」 (We entrusted the difficult repair to an experienced artisan.)
The difficult repair is entrusted to an experienced artisan. The task and the person are identified, but a successful completion of the repair is not reported.
Identify what is left to whom
A menu decision and a repair are different objects of 任せる. Do not combine the decision to leave the menu to the mother and the repair entrusted to the artisan into all tasks delegated to one person.
The first sentence reports a decision to leave the menu to someone; the second reports a past act of entrusting a repair. Neither supplies the completion of the task entrusted.
Does deciding to leave the dinner menu to the mother mean the difficult repair was also entrusted to her?
Show the answer and why
No. The first sentence concerns the dinner menu. The repair entrusted to an experienced artisan is a separate scene, and its completion is not reported.