Código sql:
Ver originalSELECT caso.id, caso.caso, caso.prioridad, caso.fecha, c1.conteo,c2.conteo,(c1.conteo+c2.conteo) total
FROM caso
INNER JOIN
(SELECT idcaso,COUNT(hi.idcaso)conteo FROM hi WHERE hi.idcaso=caso.id)c1
ON caso.id=c1.idcaso
INNER JOIN
(SELECT idcaso,COUNT(fb.idcaso)conteo FROM fb WHERE fb.idcaso=caso.id)c2
ON caso.id=c2.idcaso
No lo he probado