To travel by bus and train, you will need to take the following steps:
1. Take a bus from Carmarthen to Cardiff. The journey takes approximately 2 hours and 15 minutes and costs around £15.
2. Take a train from Cardiff to Newport. The journey takes approximately 30 minutes and costs around £10.
3. Take a train from Newport to Birmingham New Street. The journey takes approximately 2 hours and costs around £15.
4. Take a train from Birmingham New Street to Aberdeen. The journey takes approximately 6 hours and costs around £15.
The total cost of the journey is approximately £45.
There are other ways to travel from Carmarthenshire to Aberdeen, but they are more expensive. For example, you could travel by plane, but the flight would cost around £150. You could also travel by car, but the petrol and parking would cost around £120.