Math Problem Solving
statistics and probability​

Standard Deviation = 3.22

Variance = 10.36

Step-by-step explanation:

x          P(x)           x × P(x)              x²             x² × P(x)

19         0.20           3.8                  361               72.2

10         0.20             2                   100                20

11          0.30           3.3                   121                36.3

12         0.20           2.4                   144               28.8

13          0.10            1.3                   169                16.9

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                            12.8                                         174.2            => Total

Mean Formula

Variance Formula

Standard Deviation Formula

option (b) is correct

step-by-step explanation:

to find the solution of this system, we need to convert it into reduced row-echelon form. we have,

after applying row operations r2 -> r2/2 and r3 -> r3/3, we get,