Find the circumference of the circle, when the raduis is 7?

Me solve this problem, and someone clearly explain to me how to solve it.1.) use the value of the discriminant to determine if the given trinomials has 2 real solutions, 1 real solution, or no real solutions. a.  x2  − 4x  − 7 = 0b. 4r2  + 11r  − 3 = 0c. 3m2  + 7 = 0d.  t2  + 2t  + 1 = 0

:24% of students in a class are girls. if there are less than 30 students in this class, how many students are there? how many girls are there?

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.