Jamar is finding (-). find his mistake and correct it. explain your answer.

The correct answer would be (-24). When multiplying with negative integers, negative times negative is positive, however, the final answer, in this case, is negative because you are then multiplying a positive and a negative:
(-2)(-3)=6
6(-4)=(-24)
I'm guessing Jamar's mistake was he multiplied all of them thinking his answer would be a positive integer: 24. 

What's the denominator

No i refuse to tell you the answer but the estimate is 10