Which of the following expressions are equivalent to -\dfrac{9}{j}− j 9 minus, start fraction, 9, divided by, j, end fraction? Choose all answers that apply: Choose all answers that apply: (Choice A) A \dfrac{9}{-j} −j 9 start fraction, 9, divided by, minus, j, end fraction (Choice B) B -\dfrac{-9}{j}− j −9 minus, start fraction, minus, 9, divided by, j, end fraction (Choice C) C None of the above

Group A:
1 dot at 9:     1 x    9 =     9
7 dots at 10: 7 x 10 =   70
8 dots at 15: 8 x 15 = 120
8 dots at 17: 8 x 17 = 136
6 dots at 19: 6 x 19 = 114

Mean: (9+70+120+136+114) / (1+7+8+8+6) = 449/30 = 14.97

Group B:
6 dots at 10: 6 x 10 = 60
5 dots at 14: 5 x 14 = 70
6 dots at 18: 6 x 18 = 108
5 dots at 25: 5 x 25 = 125
4 dots at 28: 4 x 28 = 112
4 dots at 29: 4 x 29 = 116

mean: (60+70+108+125+112+116) / (6+5+6+5+4+4) = 591 / 30 = 19.70

The group that has a lower mean age of painting students is Group A. Its mean is 14.97 or 15 years of age.