CAN SOMEONE PLZ PLZ HELP ME? :)

6.The Martians ask you to explain one last thing, Ultimate Math Ambassador. Assign any number to x. Using complete sentences, explain whether f(g(x)) and g(f(x)) will always result in the same number. You will use the inverse function that you created in problem number 5 for g(x).

ok the functions I have are
f(x)=2+10x
and
the inverse, im not sure which one im supposed to use, I have
y=2+10x
and
f^-1(x)=x-2/10

I have no idea how to set this one up cuz Idk which one im supposed to use

Question

CAN SOMEONE PLZ PLZ HELP ME? :)

6.The Martians ask you to explain one last thing, Ultimate Math Ambassador. Assign any number to x. Using complete sentences, explain whether f(g(x)) and g(f(x)) will always result in the same number. You will use the inverse function that you created in problem number 5 for g(x).

ok the functions I have are 
f(x)=2+10x 
and
the inverse, im not sure which one im supposed to use, I have 
y=2+10x
and 
f^-1(x)=x-2/10

I have no idea how to set this one up cuz Idk which one im supposed to use