Answer: 6n+1
Process: trial and error (sorry it’s not more i. depth)
A fraction of a week in 2 days is: 2/7
Cost of book = 60
Lost book = 60 * 0.75 = 45
Equation of amount of lost book (N) = 0.75 * B
Hope this helps!
Of 33 I think that's what the question says
