Solve for k: 3(k+8) = 21

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 is the 12th term of b(n)=-4-2(n-1)

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are: