Is it safe to take an Advil (200mg) in combination with nobumetone 500mg?

There is a moderate interaction, and a therapeutic duplication as you are taking 2 NSAIDs, which could potentially be harmful to your health.

I suggest you speak with the Dr. that prescribed Nabumetone and not mix 2 NSAIDs, he/she can guide you, but never self medicate.

Interactions between your drugs
Moderate
ibuprofen nabumetone
Applies to: Advil (ibuprofen), nabumetone

Using ibuprofen together with nabumetone is generally not recommended. Combining these medications may increase the risk of side effects in the gastrointestinal tract such as inflammation, bleeding, ulceration, and rarely, perforation. Gastrointestinal perforation is a potentially fatal condition and medical emergency where a hole forms all the way through the stomach or intestine. You should take these medications with food to lessen the risk. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact. Your doctor may also be able to recommend medications to help protect the stomach and intestine if you are at high risk for developing serious gastrointestinal complications. You should seek immediate medical attention if you experience any unusual bleeding or bruising, or have other signs and symptoms of bleeding such as dizziness; lightheadedness; red or black, tarry stools; coughing up or vomiting fresh or dried blood that looks like coffee grounds; severe headache; and weakness. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

For more information click on the link:

https://www.drugs.com/interactions-check.php?drug_list=1674-0,1310-782