Can y’all help me with a b and c please

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 (%)

Explain how you can find the missing fraction in 3 4/5 / (blank) 2 5/7. then find the missing fraction.

Edger needs 6 cookies and 2 brownies for every 4 plates how many cookies and brownies does he need for 10 plates