Let the average cost of car in 2009 be $x, then the average cost of a car in 2013 is 2x - 5
25,000 = 2x - 5
2x = 25,000 + 5 = 25,005
x = 25,005/2 = $12,502.50
Keep adding by the same value everytime so start with 10,000 then add 20,000 etc
Answer: 
Step-by-step explanation:
(a) Given
Sam charge $5 for each dog for a thirty minute walk
For an hour which is double the thirty minutes, it must be double of the same charge.

(b)Given
With $20, Christie sells 100 cups of lemonade with a quarter per cup charge
For 100 cup, she generate a revenue of

So, she earns
that is , her profit is 
21 blocks, because if he uses 38 you subtract 17 and you get 21