Here is another STEP homework question, which is a famous riddle.
Puzzle. Peter had ten cows. All but nine died. How many cows are left?
The wording is confusing on purpose. So, the students who are in a hurry subtract nine from ten and answer that only one cow is left. This answer is wrong. All but nine means that one cow died. So, the correct answer is nine.
One of my students decided that nine is the name of one of the cows, though it should have been capitalized. This means that all the cows except for Nine died, and only one cow, Nine, is left.
This student managed to find a legitimate explanation for the standard wrong answer.