Answer:
Problems left to complete = 9
Step-by-step explanation:
Given that:
Number of problems on the test = 45
Percent of completed problems = 80%
Number of completed problems = 
Number of completed problems = 0.8 * 45 = 36
Problems left to complete = 45 - 36
Problems left = 9
Hence,
Problems left to complete = 9
We did this same kind of problem in school. All we did was divide the those 2 numbers to figure out the unit price. So, 20/5 = 4 $ per CD.
A. 20 for $2.47 is about 12 cents per ounce (0.1234)
32 oz for $2.99 is about 9 cents per ounce (.093)
40 oz for $3.79 is about 9 cents an oz (0.095)
B. The best deal is 32 ounce for $2.99 but not by much over 40 oz for 3.79