You can
put this solution on YOUR website! .
Since the word "now" relates to a UNDEFINED situation, I FORCED to give two answers:
- he has $19 before paying the debt,
and
- he has 19-12 = 7 dollars after that.
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When the true Math problem is formulated, it NEVER leaves a space for ambiguity.
Let it will be the major lesson for you from my post.