Currently have a project set-up for the holidays and the teacher is away from the rest of term :S
I know which formula I need for my setup (balloons into water) but am not sure on exactly how to apply the formula

My environment temperature (sink of water) is going to be constant at 10 degrees Celsius. so that is Tenv?
The initial temperature of water in the balloons is going to be 50 degrees Celsius so that is T0?
The surface area of the balloon is equal to A?
This setup is to run for 30 minutes to observe the rate of cooling.
and that is where my understanding stops.
Can someone please show working for a scenario of this?
Say a balloon with a surface area of 50cm squared and the above temperatures to determine the temperature after 30 minutes have passed
Thank you to anyone who can help