Determine if the argument is valid or invalid. Give a reason to justify answer.
If it is cold, then you need a coat.
You do not need a coat.
∴ It is not cold.

Well, what does it mean if
p implies q?
It means either p is false, or q is true, right?
Because if p is not false, or p is true, it automatically implies q is true.

p is false OR q is true.
At lease one of these statements is true, and it's NOT the second statement, because we assumed q is false.
Then it must be the case that the first statement is true (p is false)
or (It is not cold)