The library sells 500 books at its annual used-book fundraiser. They take in a total of $3940. Children's
books cost $5, and adult books cost $9. How many
children's books did they sell?
Let e = number of children's books sold, and Let
a= the number of adult books sold.
Which system of equations can the librarians use to
solve this problem?
A.
5c+9a=500
c+a=3940
c+a=500
C.
5c+9a=3940
B.
a=500-c
9c+5a=3940
a+c=500
D.
5a+9c=3940

correct choice is b

step-by-step explanation:

when you calculate the average rate of change of a function, you are finding the slope of the secant line between the two points. for the function the average rate of change from point to point can be calculated as

to find the average rate of change from day 2 to day 10, note that at day 2, 8 houses were sold, so a(2,8) and at day 10, 2 houses were sold, so b(10,2). thus,