The library sells 376 books at its annual used-book fundraiser. They take in a total of $2120. Childrens books cost $4, and adults books cost $7. How many childrens books did they sell?
Let c = number of childrens books sold, and let a = the number of adult books sold.
which system of equations can the librarians use to solve this problem?
A. 4c+7a = 376
c+a = 2120
a= 376-c
B. 7c+4a = 2120
a+c = 376
C. 4a+7c=2120
c+a = 376
D. 4c + 7a = 2120