To solve the problem of converting a temperature from Celsius (°C) to Fahrenheit (°F) using the given formula:
[tex]\[
f = \left( \frac{9}{5} \right)c + 32,
\][/tex]
we need to determine the Fahrenheit temperature [tex]\( f \)[/tex] when the Celsius temperature [tex]\( c \)[/tex] is 30.
1. Substitute the given Celsius temperature into the formula:
[tex]\[
f = \left( \frac{9}{5} \right) \cdot 30 + 32
\][/tex]
2. Calculate the multiplication:
[tex]\[
\left( \frac{9}{5} \right) \cdot 30 = \frac{9 \cdot 30}{5} = \frac{270}{5} = 54
\][/tex]
3. Add 32 to the result:
[tex]\[
f = 54 + 32 = 86
\][/tex]
Thus, when [tex]\( c \)[/tex] is 30, the temperature in Fahrenheit [tex]\( f \)[/tex] is 86.
Therefore, the correct answer is:
(C) 86
