SQL Query Rewrite

I need to create a query that will return results based on set criteria and then basically count the number of results it returns to input into a graph.

This is what I have that works, but is sometimes slow,

SELECT MAX(complete_date) FROM projects_questions

INNER JOIN report_answers ON report_answers.question_id = projects_questions.id

INNER JOIN projects_reports ON projects_reports.visit_id = report_answers.visit_id

INNER JOIN retailers_addresses ON retailers_addresses.id = projects_reports.store_id

WHERE

projects_questions.question_text = '".$data_questions['question_text']."'
AND
projects_questions.attr_id = '".$data['id']."'
AND
answer = '$ans'
AND projects_reports.complete='1'

GROUP BY projects_reports.store_id;";

This will basically return any rows that have the answer defined by $ans AND the survey is complete AND belongs $attr_id group AND question_text matching.

We basically visit stores to get survey feedback, so the above needs to ensure only the last entry for a store is shown.

I also need to add a sub query to ensure that the store was asked the question (some asked in some stores and not in others)

I tried to achieve this using the below within the WHERE clause, it seems to work possibly but is extremely slow.

retailers_addresses.id IN (SELECT store_attribute_assign.attr_id FROM store_attribute_assign WHERE store_attribute_assign.attr_id = '".$data['id']."')

Im looking for someone to rewrite or even split if it will work out faster.

I need this doing ASAP!!!