There was a bit more confusion on Question 6. The most important thing to know is that the numbers you were asked to multiply or divide were written in scientific notation. This is important, because it influences how the multiplication and division works.
Also, I have to apologize for the fact that part 6.5 was ambiguous. There were two valid ways to interpret that question, and I counted either as correct. Please look at the worked-out version below.
Here's the other interpretation:
I'm sorry for the ambiguity -- I didn't see it until I started grading homeworks, and it became clear it could be interpreted either way.