**Rectification of Errors:**

a) **Cheque received from Lala Ram credited to Tika Ram's account and debited incorrectly to cash account:**

This error can be rectified by following the below steps:

1. **Identify the error:** The error in this case is that the cheque received from Lala Ram was credited to Tika Ram's account instead of being credited to the cash account.

2. **Rectification entry:** To rectify this error, we need to reverse the incorrect entry and make the correct entry. The rectification entry will be as follows:
- Debit Tika Ram's account and credit Cash account with ₹75.

**Rectification Entry:**
Tika Ram's account Dr. ₹75
Cash account Cr. ₹75

3. **Explanation:** By debiting Tika Ram's account and crediting the cash account with ₹75, we are reversing the incorrect entry and making the correct entry. This rectifies the error and ensures that the accounts are stated accurately.

b) **Goods returned by Chandmal Bros included in stock, but not recorded in the books:**

To rectify this error, we need to follow the below steps:

1. **Identify the error:** The error in this case is that the goods returned by Chandmal Bros were included in the stock, but no entry was made in the books to reflect this return.

2. **Rectification entry:** To rectify this error, we need to make the correct entry to reflect the return of goods. The rectification entry will be as follows:
- Debit Stock account and credit Purchase Returns account with the value of goods returned (₹150).

**Rectification Entry:**
Stock account Dr. ₹150
Purchase Returns account Cr. ₹150

3. **Explanation:** By debiting the stock account and crediting the purchase returns account with the value of goods returned (₹150), we are rectifying the error and ensuring that the books reflect the correct information. This rectification entry adjusts the stock value and accurately represents the return of goods by Chandmal Bros.

By following the above steps and making the necessary rectification entries, we can rectify the errors mentioned in the given scenario and ensure that the accounts are stated accurately in the books.