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?
Given b = 1/5 j
b+4 = 1/3 ( j -4) sub in the red equation
1/5j + 4 = 1/3 ( j-4)
1/5 j + 4 = 1/3 j - 4/3
3/15 j + 4 = 5/15 j - 4/3
-2/15 j = -4 - 4/3
j = 40 initially she gives away 4 to have 36 left