The temperature of a mixture changes by -5.2 Fahrenheit between 8am and 11am. At 6pm the temperature is 14.5 Fahrenheit, which is half of what it was at 11am.

What was the temperature at 8am of the mixture.

I have this equation , but not sure is correct.

1/2(x-6.8)= -3.1Can you help me create a equation. Mine is wrong.