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What expression is equivalent to 42x-56y

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

He weights of 2-pound bags of best dog food are approximately normally distributed with a given mean  and standard deviation  according to the empirical rule, what percentage of the bags will have weights within 3 standard deviations of the mean? 47.5%68%95%99.7%