I believe pints would be a good unit to use, since most people drink around 100 ounces a day, and one pint is about 16 ounces.
According to the Scientific Method (the scientific process you use to go about figuring out the answer to a question) is:
1. Ask a Question
2. Do Background Research
3. Construct a Hypothesis
4. Test Your Hypothesis by Doing an Experiment
5. Analyze Your Data and Draw a Conclusion
6. Communicate Your Results
Answer:
C. 1.2x
Step-by-step explanation:
He pays 1 x for his haircut, and an additional 20% on top of that, or an additional 0.2x. If you write that as an expression, you can simplify it like this:

You can also work it out by multiplying by 1.2 as stated in answer C. If his haircut costs $10, adding a 20% tip of $2 is the same as multiplying by 1.2.
