To find the rate of text messages per hour, you can start by calculating the number of messages received in 1 minute, and then scale that up to an hour.
You received 9 messages in 12 minutes, so the rate per minute is: \[ \text{Rate per minute} = \frac{9 \text{ messages}}{12 \text{ minutes}} = 0.75 \text{ messages per minute} \]
To find the rate per hour (60 minutes): \[ \text{Rate per hour} = 0.75 \text{ messages per minute} \times 60 \text{ minutes} = 45 \text{ messages per hour} \]
So, the rate of text messages is 45 messages per hour.