Answer:
55 - 4m = x
Explanation:
This expression shows how much money Lily has left.
This is because, if Lily received $55 for her birthday, and she used some of her money to buy 4 pencils that cost m each, 5 minus 4 multiplied by the amount of money each one costed equals the amount that she has left.
Therefore, the correct expression is 55 - 4m = x.
Hope this helps! :D