Write a function to convert Celsius to Fahrenheit using F=(9/5)C+32. Find the Fahrenheit value when C=56.7 and when C=−89.2. (The record high and low temperatures ever recorded on Earth.)
If x is the given temperature in Celsius, the function to return the equivalent temperature in Fahrenheit it:

f(x) = 9 / 5 * x + 32
f(x) = 9/5x + 32
f(x) = 9/5 * (x + 32)
f(x) = 9/5c + 32

The value in Fahrenheit at C=56.7 (a record high) is:
?

The value in Fahrenheit at C=−89.2 (a record low) is:
?

Using your function, f(C), to convert Celsius to Fahrenheit, compare the difference at C=20 between the function value and the simpler function: g(C)=2C+30. (In other words, is "double and add 30" a reasonable approximation?)

The difference f(C)−g(C) at C=21 (approximate room temperature) is:
?