A thick swarm of flies filled the palace. Pharaoh told Moses, “Hurry and pray for me.” Moses pleaded with the Lord to remove all the flies and the Lord did as Moses asked (from Exodus 8:20-32).
God answers specific prayers.
A Blog on Prayer
For People Who Pray
A Blog on Prayer 
I don’t remember that verse from Exodus. I’ll have to back read that.
“The Lord did as Moses asked. . . Not a single fly remained (Exodus 8:31 NLT).”