Ruby and her children went into a bakery and she bought $18 worth of donuts and cookies. Each donut costs $1 and each cookie costs $1.50. She bought a total of 15 donuts and cookies altogether. Graphically solve a system of equations in order to determine the number of donuts, x, x, and the number of cookies, y, y, that Ruby bought.

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Is experimental probibilty the same as the observed frequency in math? i need the answer asap!

The weekly amount spent by a company for travel has an approximately normal distribution with mean = $550 and standard deviation = $40. a) what is the probability that the actual weekly expense will exceed $570 for more than 20 weeks during the next year? (note: one year = 52 weeks) b) what is the probability that actual weekly expenses exceed $580 for 10 or more, but 16 or fewer weeks during the next year?