It is 03:20 on a weekday night shift in a district general Emergency Department.

A 58-year-old man presents with 90 minutes of central crushing chest pain, radiating to his left arm, associated with diaphoresis and nausea. He has a background of hypertension and is an active smoker. There is no history of previous myocardial infarction.

An ECG demonstrates ST-segment elevation in the inferior leads. Primary PCI is unavailable within the recommended timeframe, and the patient receives intravenous thrombolysis in accordance with local and national guidelines.

During post-thrombolysis counselling, a junior doctor asks you to help interpret outcome data from a large randomised controlled trial comparing thrombolysis with standard care.

The trial reports the following 30-day mortality outcomes:

Control group mortality: 12%

Thrombolysis group mortality: 9%

Based on these data, what is the Number Needed to Treat (NNT) to prevent one death at 30 days?