A Contract Under Deceitful Circumstances

Maine socha thoda tricky lagta hai, lekin ab thoda clear dikhta hai. Question aaya tha: "X signs an agreement with Y to buy a plot of land for ₹5 lakhs, but X thinks he is buying a 10-marla plot, actually Y sold a 5-marla plot. X pays ₹2.5 lakhs as advance. X comes to know about the deceit, and X returns the money. Kya Xkaun case mein aapka adhikar hai? Aur Y par kya action leya ja sakta hai?"

This one mein main samajhata tha ki X ki agreement vikalp karne ka adhikar hai, lekin ab main samajhta hoon ki X ka adhikar nahi hai.