A history class is made up of 12 tenth-graders and 9 eleventh-graders. The tenth-graders averaged 77 on the midterm exam and the eleventh-graders averaged 91. What was the
average grade on the midterm exam for the entire class?
A. 82
B. 83
C. 84
D. 85

step-by-step explanation:

the true ones are a b and d

25.3

step-by-step explanation:

1st step

add 3+6

=9

multipy 9*3

=37

step-by-step explanation:

we have

using a graphing tool

see the attached figure

this is a quadratic equation (vertical parabola) open up

the vertex is a > vertex

the domain of the function is all real > interval (-∞,∞)

the range of the function is the > [-6.125,∞)

the function has two x->   and

the function is increasing over the > (0.25,∞)

the function is decreasing over the > (-∞,0.25)

step-by-step explanation:

the answer is in the picture