Did something wrong in my calculations, but I don't know what.

Should end up in the form

I got my answer in that form and the values are correct for A, B, C, and D. But when I use it to answer the rest of the questions I'm getting wrong answers. I think I did something wrong in the beginning when getting it in that form.

Can someone go through the steps and give me your answer to check with mine. I need to see what I did wrong.

A = -30

B = 6

C = 6

D = 6

Can you display your final answer in the form: