How to calculate propagation of errors?

I have a first year physics assignment, and I am completely lost.

Pfinal = 605 ± 5 Pa
Pinitial = 521 ± 5 Pa

the question is : ΔP = Pfinal -Pinitial

How do I do this!!? Any help would be greatly appreciated. Thank You :)

When I use an online propagation calculator, I get ΔP = 84 ± 7
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