Round to the nearest percent. From 13 friends to 17 friends

please help! Thank you!

Researchers are conducting experiments to determine the role of alcohol in the development of depression. after the study is complete, they determine that the relative risk of developing depression is 1.55 with a 95 % ci of 1.2 -1.9. each group is then divided into nonsmokers and smokers. the relative risk for the nonsmokers is 1.12 with a 95% ci of 0.87-1.37. the relative risk for the smokers is 1.7 with a 95 % cl of 1.5-1.9. what type of bias may affect this study? a. procedure bias b. recall bias c. selection bias d. confounding e. lead-time bias

How many and of which kind of roots does the equation f(x)=x3−x2−x+1

Lines a and b are perpendicular. if the slope of line a is 3, what is the slope of line b?