I dont get it- pls help

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?

Math i have no idea how to do a and b

Identify the statement below as either descriptive or inferential statistics. upper a certain website sold an average of 117 books per day last week. is the statement an example of descriptive or inferential statistics? a. it is an example of descriptive statistics because it uses a sample to make a claim about a population. b. it is an example of inferential statistics because it uses a sample to make a claim about a population. c. it is an example of inferential statistics because it summarizes the information in a sample. d. it is an example of descriptive statistics because it summarizes the information in a sample.