Answer:
8. $21 is your constant number, so nothing changes. $5.50 is a number that changes based on how many months have passed. So your equation should be: 21 + 5.50x
9. Since the number 7 is a percentage in this problem, it should be written as .07. Since the total price is unknown, it should be written as x. By using the equation x * .07, you have the amount that should be added to the total price. The final equation should be x * .07 since you have an unknown total price.
10. f(x)= means the same thing as y=, so they should be treated the same. Since f(x)=14, you should plug it into the equation (by putting 14 into any place that you see an x) , giving you f(14)=1/4(14)+10. The final answer should be f(14)=13.5 or f(x)=13.5
11. The dependent variable should be the three facts since they're dependent on the people listed. If they wasn't any people listed, there wouldn't be three facts, therefore making the people listed the independent variable.
Hope this helped!