Answer:
The error is at step (3) .
The correct step (3) will be,

=
[by using the laws of indices]
All other steps are correct.
Step-by-step explanation:
The error is at the step (3) , because the student has tried to prove the quotient rule of logarithms by using the property i.e., 'The quotient rule of logarithm' itself , i.e. ,by assuming the property does hold before proving it. So, the proof is fallacious.
The correct step (3) will be,

=
[by using the laws of indices]
All other steps are correct.
Answer:
It is a solution
Step-by-step explanation:
8d+6= -8d-186
Add 8d to each side
8d+8d+6= -8d+8d-186
16d +6 = -186
Subtract 6 from each side
16d +6-6 = -186 -6
16d = -192
Divide each side by 16
16d/16 = -192/16
d = -12
It would be $44.8 I think