Cd = dc x + 13= 13 + x
4 (2x - 3) = 4 (2) - 4(3)
2+(a +b) = (2+a) + b
Please help me I will give brainliest, thanks and a lot of points

Will give brainliest sum of arithmetic series (sigma notation) find the numerical answer to the summation given below. (image shown below)

Which statements regarding the diagram are true? check all that apply.

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?