You just have a simple calculation error when you add 4 to -4/3, 4 = 12/3. 12/3 - 4/3 = 8/3
I'm unsure about this question:
Then adding four to both sides:
Then I multiply both sides by three to get rid of the fractions, leaving me with
But according to the book, the final answer should have a positive eight rather than a negative eight. I'm not sure how to arrive at this answer (something to do with the first step in my working... is there a double negative on the right hand side?). Any help would be appreciated.