The answer is true.
Method 1:
The given function is a cubic function. And inverse of a cubic function is also a function.
Method 2:
Since the function is one-to-one function i.e it passes the horizontal line test, its function will pass the vertical line test which is a test if a relation is a function or not.
So, yes the inverse of G(x) will be a function.
3x - y = 9
4x + y = 5
---------------add
7x = 14
x = 14/7
x = 2
3x - y = 9
3(2) - y = 9
6 - y = 9
-y = 9 - 6
-y = 3
y = -3
C. (2,-3) is a solution to the system of linear equations