Since the question has the word "about" in it, therefore it is asking for an estimate of the correct answer.
Due to this, let us round the market price of the poster to $16.00.
The question states that the poster is 10% of the market price. This means that it is as expensive as it would normally be. Let us then solve for the price Mia paid by multiplying the two together:
This shows us that Mia actually only paid about $1.60 for the poster that she bought.