Pls help on all three this is my homework

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 (%)

You buy five cds at a sale for $5.95 each. write an expression for the total cost of the cds.then use the distributive property and mental math to evaluate the expression.

If you prove that ∆wxz is congruent to ∆yzx, which general statement best describes what you have proved?