In a normal distribution, 99.7% of the data fall within how many standard deviations of the mean?

Use the knowledge of x- and y- intercepts to choose the correct graph of the equation 3x+6y=6

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The rectangle shown has a perimeter of 108 cm and the given area. its length is 6 more than five times its width. write and solve a system of equations to find the dimensions of the rectangle.