Question

Adam and Edwin spend a certain amount of money from their money box each month to buy plants. The table shows the relationship between the amount of money (y) remaining in Adam's money box and the number of months (x): Function 1: Number of Months (x) Amount Remaining (dollars) (y) 1 90 2 83 3 76 4 69 The equation shows the relationship between the amount of money, y, remaining in Edwin's money box and the number of months, x: Function 2: y = –9x + 90 Which statement explains which function shows a greater rate of change? Function 2 shows a greater rate of change, because Edwin spends $90 each month and Adam spends $21 each month. Function 2 shows a greater rate of change, because Edwin spends $9 each month and Adam spends $7 each month. Function 1 shows a greater rate of change, because Adam spends $21 each month and Edwin spends $81 each month. Function 1 shows a greater rate of change, because Adam spends $7 each month and Edwin spends –$9 each month.

Answer 1

The answer would be choice 2 : Function 2 shows a greater rate of change, because Edwin spends $9 each month and Adam spends $7 each month.
I found this out because for Adam, you simply subtract the y-coordinates from each other and get 7 each time. Edwin clearly shows that he Spends $9 each month with the negative sign.