• Seeta, Rajinder and Surinder are children of Mr. and Mrs. Aggarwal.
• Renu, Raja and Sunil are children of Mr and Mrs. Malhotra.
• Sunil and Seeta are a married couple and Ashok and Sanjay are their children.
• Geeta and Rakesh are children of Mr. and Mrs. Gupta.
• Geeta is married to Surinder and has three children named Rita, Sonu and Raju.
Renu is Sanjay's ................
Sister-in-law
Step 1: Place Renu in the correct family.
Renu, Raja, and Sunil are children of Mr. & Mrs. Malhotra. Hence Renu is Sunil's sister.
Step 2: Connect to Sanjay.
Sanjay is the son of Sunil and Seeta \(\Rightarrow\) Renu is Sanjay's father's sister.
Step 3: Name the relation.
Father's sister is \(\boxed{\text{Aunt (Aunty)}}\).