Answer:
13<x-21
(No correct option, unless the last option is incomplete and would be 13<x-21)
Explanation:
The sentence is:
13 is less than x minus 21
We need to know that some expressions are related to some symbols to make equations:
"is less than" is the symbol "<", and
"minus" is the symbol "-".
So, writting the expression as an inequation (it's an inequation because of the symbol "<"), we have:
13 < x - 21
So there is no correct answer, unless the last option is incomplete (if the last option is not just 13, and is 13<x-21, that would be the correct option)