Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:

Convert text to sql: What is the average sales of the journals that have an editor whose work type is 'Photo'? | journal : journal_id , date , theme , sales | editor : editor_id , name , age | journal_committee : editor_id , journal_id , work_type | journal_committee.journal_id = journal.journal_id | journal_committee.editor_id = editor.editor_id | 

### Response:

select avg ( _ ) from _ where _ | select avg ( journal.sales ) from journal join journal_committee on journal.journal_id = journal_committee.journal_id where journal_committee.work_type = 'Photo'