Im a little confused I need some help with this ez subtraction (math) problem.?

ok its a word problem if you have $16.00 on line 20 and you have $19.00 on line 15 and my question is when its asked you subtract line 20 from line 15 which number goes on top in the problem...call me dumb (dont care) just want an answer ....thanks for your help in advance!