B.
Elements of the same group in the Periodic Table will have similar chemical and physical properties.
First we need to count the total number scores. This can be done from the stem and leaf plot. The total number of scores are 19. The total number of values is odd, so the median position will be:

Thus the 10th score is the median score for the class of Mr. Robert. The 10th score from the stem and leaf plot is 81.
Thus 81 is the median score of Mr. Robert's Class.
Answer:
(x-20)(x+3)
Step-by-step explanation:
Answer:
A-3, B-4, C-1, D-2
Step-by-step explanation:
A:
- 5x-(3x+1)
- Expand, 5x-3x-1
- Combine like terms, 2x-1
B:
- 5x-(-3x-1)
- Expand, 5x+3x+1
- Combine like terms, 8x+1
C:
- -5x-(3x+1)
- Expand, -5x-3x-1
- Combine like terms, -8x-1
D:
- -5x-(-3x-1)
- Expand, -5x+3x+1
- Combine like terms, -2x+1