what is the mistake in this problem?

Answer:
The mistake is that 54 was not subtracted from both sides. It should be. Also, I have no idea what those shenanigans with the -3b = 60 simplification is, but you have to divide both sides by -3. b = 16
Step-by-step explanation:
This is how this is supposed to be solved.
54 - 3b = 6
-54 -54
-3b = -48
(-3b)/-3 = -48/-3
b = 16