If you double radius of a circle, how does this affect the area of the circle

What is the anwers for 9+2x=5x-3-x

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?

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