Can you help me with #7 based on the top instructions

Recognizing Proportional Situations For each problem below: a. Solve for the quantity requested. b. Determine if the two variable quantities are proportional or not. c. If the quantities are proportional, identify what ratio remains constant. Include units. If they are not proportional, show with sample numbers that the ratio does not remain constant. d. Choose letters to stand for the two variable quantities and write an equation relating them. Test your known data to be sure it accurately reflects the problem situation. Example: If Meg works 10 hours she earns $220. If she works 20 hours she earns $440. How much does she earn for working 15 hours? a. 5330 b. Yes, the it hours worked and the it dollars earned are proportional. c. $220/ 10 hours = $440/ 20 hours =522f1 hour or $22 per hour. d. Let D = # dollars earned and H = if hours worked. D = 22(H) check: $220 = 22 (10) 1. Mary buys 2 1/2 pounds of apples for 55. Jenny gets 4 pounds of apples for $8. How many pounds can be bought for $15? 2. A box of cereal costs $4.00 for a 10-ounce box and $6.50 for a ZD-ounce box. How much would a 30-ounce box cost? (Hint: you can solve this if you assume the cost of the package is the same regardless of the amount of cereal inside the box; assume the increase in price from 10 to 20 to 30 ounces is only due to the additional amount of cereal.) 3. Ten inches equals 25.4 cm; one hundred inches equals 254 cm. How many cm are in a yard? 4. A child's mother pays him 50 cents for each 15 minute chore he does. How long does he have to work to earn $4? 5. It costs Rita 50 cents for the first three minutes of a long-distance phone call to her boyfriend and 20 cents for each additional minute. How much does it cost Rita to talk to him for 12 minutes? 6. A circular pizza with diameter 6" has 28.26 square inches of area. An 8" diameter pizza has 50.24 square inches of area. How much area does a 10" diameter pizza have? 7. If Marvin averages 30 miles per hour on the drive to his parents' house it will take him 40 minutes. How long will It take him if he averages 50 miles per hour? Give your answer in minutes. (Hint: Figure out how many miles away his parents' house is.) How do the equations for proportional situations differ from the equations for nonproportional situations? Clarify your answer using your equations from the problems above