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Which of the following system of equation is not equal to the system of equations is not equal to the system of equations shown below

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?

25) 56(1) = 5b a. identity property of addition b. identity property of multiplication c. commutative property of multiplication d. commutative property of addition