Please answer This Question I Need HElp

Please someone answer this question

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 (%)

Find the value of x. round the length to the nearest tenth

Present age of man is 45 years, 5 years back his age was 4 times age of his son what is present age of his son?