Ask Me Help Desk - I'm getting the wrong answer

$ \text{start with your equation}\\ \frac 3 5 = \frac 1 {1-r} \\ \text{flip both sides} \\ \frac 5 3 = \frac {1-r} 1 \\ \text{simplify the right and subtract 1 from each side} \\ \frac 5 3 - 1= -r \\ \text{divide by -1} \\ -\frac 5 3 + 1 = r \\ \text{simplify left hand side} \\ -\frac 2 3 = r $

so, assuming that I've read your initial problem correctly then your answer of -2/3 is correct :) and the book is wrong :mad: . Enter -2/3 as your answer and send your teacher here if (s)he says you're wrong. :)