Step 1 :Let's denote the amounts of the three parts of the investment as x, y, and z for the first, second, and third part respectively.
Step 2 :We know that the total investment is $92,000, so we have the equation \(x + y + z = 92000\).
Step 3 :The total interest from the investments was $7200, so we have the equation \(0.08x + 0.06y + 0.09z = 7200\).
Step 4 :The interest from the first investment was 4 times the interest from the second, so we have the equation \(0.08x = 4 * 0.06y\).
Step 5 :Solving these three equations, we find that \(x = 54000\), \(y = 18000\), and \(z = 20000\).
Step 6 :Final Answer: The first part of the investment was \(\boxed{54000}\). The second part of the investment was \(\boxed{18000}\). The third part of the investment was \(\boxed{20000}\).