Question 251067
You need to use algebraic division outlined here 

http://www.purplemath.com/modules/polydiv3.htm

The example to follow is 3x^3 – 5x^2 + 10x – 3  by  3x + 1 because this gives a remainder as in your problem.

The answer to your problem is 7b^2-2b+8 + (3/6b+2)

Have a go at the steps and see if you can get the answer. Write back if you need help with the stages.

I will give you the first stage. Divide 6b into 42b^3 gives 7b^2.