No links will mark brainliest if correct!

Need on this geometry question. explain how you did it.

Which one ? is the answer and how to find this answer

Acompany that manufactures and sells guitars made changes in their product range. from the start they had 20 models. then they reduced the number of models to 15. as a result, the company enjoyed a 10% increase in turnover. - how much did the stock level change? in (%)