Answer:
he made the error in step 3
Explanation:
Charlie did indeed do the first steps correctly. He took like terms to one side. However, when he added 2p and 6 to get 8p (?) he mistook them for like terms. This is incorrect. 2p cannot be added with 6 because they are different terms: one with a variable, and one without anything. He should've continued the process of isolating p, the variable, by subtracting 6 from both sides, having:
-11 - 6 = 2p +6 - 6
simplify:
-17 = 2p
Isolate:
p = -17/2