g(x) = 0.4x - 1.8
Since the output, or g(x), is 4.6, substitute that number in for g(x).
4.6 = 0.4x - 1.8
Add 1.8 to both sides of the equation.
4.6 + 1.8 = 0.4x - 1.8 + 1.8
6.4 = 0.4x
Now, divide 6.4 by 0.4.
The answer is x = 16. The output is also x.
