Final answer:
To convert 66°F to Celsius, use the formula C = 5/9 * (F - 32) and plug in the value of F as 66 to get approximately 18.9°C.
Step-by-step explanation:
To convert from Fahrenheit (°F) to Celsius (°C), use the formula: C = 5/9 * (F - 32).
Let's apply this formula to convert 66°F to Celsius:
C = 5/9 * (66 - 32)
C = 5/9 * 34
C ≈ 18.9
Therefore, 66°F is approximately 18.9°C.