Please solve this l am in many problem please please please please help me ​

Jenisey has $24 to spend on seven pencils. after buying them she had $10. how much did each pencil cost.?

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 (%)

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way