What is the range of the given function?

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?

What percent of 18 is 24? and plz explain thx.

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