Final answer:
To write the sentence as an equation, use the formula '165 - d = 240' where d represents the unknown quantity being decreased.
Step-by-step explanation:
To write the sentence as an equation, we need to assign a variable to the unknown quantity. Let's say the unknown quantity is d. The sentence '165 decreased by d is the same as 240' can be written as:
165 - d = 240
Learn more about writing an equation for a sentence