"Find ten apples and oranges" Do I find 10 or 20?

I think its ambiguous. If the question was:

"Find ten apples and ten oranges." this is no ambiguity.

It is the writer's responsibility to communicate clearly and without ambiguity.

If you have to struggle to determine which of three or four possible questions is actually being asked, it's not YOUR fault, it's his.

And can be both a distributive coordinator and a joint coordinator. So, for example, if a subject includes a distributive and, then the predicate applies equally and distinctly to both noun elements:

John and Mary live in London

means

John lives in London and Mary lives in London.

A subject including a joint and cannot be expanded in this way. So,

John and Mary are a happy couple

is incoherent as

John is a happy couple and Mary is a happy couple.

Often, however, there is no way to reliably interpret if the and is a distributive coordinator or a joint coordinator. For example:

John made cheese and cucumber sandwiches.

Did all the sandwiches consist of both cheese and cucumber (joint coordination) or did he make cheese sandwiches and also make cucumber sandwiches (distributive coordination)?

The OP's sentence Find ten apples and oranges is ambiguous in the same way.

There is a brief discussion of distributive / joint coordination in The Handbook of English Linguistics (Aarts).