Hard questions (for me anyway) pls help

Which of the binomials below is a factor of this trinominal? x^2-13+30

Stu and ambrose are working together on a study of whether diet is related to students' mental health. first, they randomly select 10 students from the student center and 10 students from the office of counseling and psychological services. then, they ask students to rate their diet in terms of healthiness on a scale of 1-100 before completing a 20-item mental health survey. a) name one of the constructs being studied b) how was the construct you named above operationally defined in this experiment? e) was the variable you described above their independent variable, their dependent variable, or a controlled variable? d) what is a confounding variable? what is a potential confound in this study?

Acontainer full of water weighs 15.5 lbs. when ¼ of the water is poured out, the container now weighs 12 ½ lbs. how much does the container weigh when empty?