Could you please help me and check my answers?

Question

Find the domain of the function.

f(x)=-8x-2
-I got the domain being (negative infinity, postive infinity).

g(x)= 3x/(x^2 -49) (I got (-inifinity,-7)U (-7,7) U (7, +ininfinity) The U is the union symbol.

Find the domain of the composite function f * g.

12. f(x)=x+3, g(x)=1/(x+7) I got (-inifinity, + inifinity) but would it be ((-inifinity,-7) or (-7,+inifinity)

15. f(x)=7x+70, g(x)=x+2 I got for this one ((-infinity,-12) or (-12,+inifinity))