205: Missing whitespace between key and answer

You started a line with curly brackets { } which turns the block into a multiple-choice question and marks an option in it. An option consists of a key enclosed in curly brackets and an answer, separated by whitespace. In your case, a whitespace character is missing.

Solution

Make sure to leave whitespace between the key and the answer in a multiple-choice option. A single space after the right curly bracket is enough:

{x} 42