Plsss help me with this:(

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

Organic apples are on special for $1.50 per pound. does total cost vary inversely or directly with the number of pounds purchased? find the cost of 3.4 pounds of apples. a. inversely: $5.10 b. directly; $5.10 c. inversely: $2.27 d. directly; $2.27

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.