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Assuming the five frame is for the number five (5) then place 5 counters in the frame.
Answer:
The step 4 is not what he should have done. But the wrong is step 5, because if he added -2x both sides, it would give the following equation:

and not 
Note that in step 4 he should have added 2x and not -2x to both sides, but we still have the equality. The problem is that step 5 is totally wrong.
I don't know what answer is expected to this question, but I would mark step 5, because this is mathematically wrong.
Solving the equation

Using distribution

Add
both sides


Add 12 both sides

Divide both sides by 5

They sold 2000 student tickets and 0 regular tickets
Answer: y = 0.5x - 2
Step-by-step explanation: 0.5x = half of a number X