Ben had 1/5 as many books as Jann. After Jann gave Ben 4 books, Ben had 1/3 as many books as Jann. How many books did Jann have in the end?
b = 1/5 j
b+4 = 1/3 (j-4) sub in the first equation
1/5 j + 4 = 1/3 (j-4)
4 + 4/3 = 1/3j - 1/5j
j = initially = 40 then she gave away 4 to have 36 books at the end