Question 1043635
x books were brought to class.
y=number of students in the class.
x-5y=15
x-7(y-5)=0.  This means that 5 fewer than y students each took 7 books.
Therefore, x=7(y-5)
Substitute into first equation.
7(y-5)-5y=15
7y-35-5y=15
2y=50
y=25
x-125=15
x=140 books.  A
There are 25 students.
If each student takes 5 books, 125 are taken and 15 are left
If 20 students (5 fewer than 25) take 7 books, none is left.