SELECT DISTINCT a.idd FROM table_a a

LEFT JOIN
(
 SELECT bid, SUM(price) AS summ
 FROM table_b
 GROUP BY bid
) b ON a.id = b.bid

LEFT JOIN
(
 SELECT cid, SUM(cash) AS summ
 FROM table_c
 GROUP BY cid
) c ON a.id = c.cid 

WHERE COALESCE(b.summ,0) != COALESCE(c.summ,0);