A solitary strike from prolific forward Ruben Castro gave Real Betis a 1-0 home win over Levante that practically ensures the Seville club will avoid relegation.The 34-year-old headed home Alvaro Cejudo's cross in the 81st minute to grab his 17th goal of the season and give the hosts a win they scarcely deserved.The win takes Betis to 37 points, nine above the relegation zone with six games remaining, while Levante sit bottom of the table on 25 points, three from safety, after a third straight defeat.Levante dominated the first half and should have taken the lead, with midfielder Joan Verdu spurning two clear chances and Giuseppe Rossi hitting the side netting.Defender Carl Medjani's header from a corner was then tipped over the bar by Betis goalkeeper Antonio Adan.The home side improved after the break and had the better of the chances, and took the lead at the ideal time, Castro escaping his marker to meet Cejudo's cross.