So I went back and reworked it.
For a) I did the synthetic division and got "x = 1,2, -3" for my final answer.
For b) Don't want to be rude, but my answer was correct. Your mistake was in the underlined part (-1)^3 -7(-1)+ 6= -1-(-7)+ 6= 12. Subtracting a negative (when you just subtracted...