Can you plzz help me on my others ones I’m begging you

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 (%)

Simplify this expression. 8x 16(x + y)

Why is causation so much more difficult to prove than correlation?