You are writing books for company X

1. X company received the contract of 100,000
No Financial transaction hence no accounting entries or
Dr. Accrued income 100,000
Cr. Sundry creditors 100,000

2. Received Advance payment of 20,000
Dr. Cash
Cr. Supplier a/c

Dr. Sundry Creditors
Cr. Accrued income

3.X company gave the sub contract to Y company 50,000
No Financial transaction hence no accounting entries or
Dr. Sundry Debtors
Cr. Y Company's account

4.X Company paid the advance to Y 10,000
Dr. Y Company account
Cr. Cash/Bank account