Hey! Im stuck on my uni calculus assignment... couple of questions i just cant get my head round! if anyone can help id be forever grateful :-)

11. A shop owner needs to calculate the cost of an item including the sales tax of 12%.
Before tax, the shop gives a discount of 8% on the original list price of the product.
(Total 7 marks; 2,3,2)
a. Write an equation that connects the total cost C of the product with the list price X.
b. If the shop owner initially puts a mark up of 100% to arrive at the list price,
what is the net profit or loss for the owner. Assume a list price of $100.
c. Using the symbols above, write the equation for net profit.

16. A certain medicine reduces the bacteria present in a person by 10% every hour.
Initially 100,000 bacteria are present. Make a table of values for the number of bacteria
present at the end of each hour for 8 hours.
a. Plot the graph of Time Vs Bacterial count on a graph paper. Use appropriate scales.
b. Approximately in how many hours will the bacterial count drop to 25000?
c. Use algebraic method to calculate the time (in hours) when the bacterial count will be 1000 or below?

jennie xx