How to set up this combining functions problem?

I think it is function f: an input of 1, gives output of -3, and an input of -4 gives output of -1. Same with g: input of 1 gives output of -3, and input of -3 gives -4 out.
So it looks like (f + g)(1) is the same as f(1) + g(1).
http://www.mathsisfun.com/sets/functions-operations.html
Well it just so happens that f(1) = -3, and g(1) = -3 so we have -3 + -3 = -6

f(1) = -3 and g(1) = -3

(f＋g)(1)
= f(1) + g(1)
= (-3) + (-3)
= -6

Confusion is good. Hopefully, out of confusion clarity will come.

f = {(1, -3) (-4, -1)}
g = {(2,5) (-3, -4) (1,-3) (0, -2)}

Find (f + g)(1)

This is not standard notation.

f takes 1 as input and produces -3 as output. It *maps* 1 to -3.
f(1) = -3

g takes 1 as input and produces -3 as output. It *maps* 1 to -3.
g(1) = -3

f(1) does not have to equal g(1). In this case it happens to be the same.

(f + g)(1) ≡ f(1) + g(1) = -3 + -3 = -6