Can someone explain me the answers?

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?

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog

What is the value of x in the equation7x+2y=48 when y=3