Sofia's mistake in finding the inverse function was in step 4. She incorrectly multiplied each side by 3 instead of 8. The correct inverse function is

Sofia's mistake in finding the inverse function was in step 4. She incorrectly multiplied each side by 3 instead of 8. The correct inverse function is

Sofia made a mistake in step 4. She should have multiplied each side by 8, not 3.
The steps for finding the inverse function of f are as follows:
1. Replace f(x) with y.
2. Switch the x and y variables.
3. Solve for y.
4. Replace y with

Sofia's steps 1-3 are correct. However, in step 4, she multiplied each side by 3 instead of 8. This is incorrect, as it will not produce the correct inverse function.
To correct the mistake, Sofia should multiply each side of step 4 by 8, giving:
8x = 3y + 4
Subtracting 4 from each side and then multiplying each side by 3 gives:
24x - 12 = y
Replacing y with
gives the correct inverse function:
24x - 12 =

Therefore, Sofia's mistake was in step 4, where she multiplied each side by 3 instead of 8.