What conclusion can you draw about the similarity of two triangles when two side lengths are proportional by the same ratio and the included angle is congruent?

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 (%)