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Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

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?

The john nash mall used 17,4000 kilowatt hours in may, with a peak load of 92 kilowatts. the demand charge is $5.95 per kilowatt, and the energy charge is $0.08 per kilowatt hour. the fuel adjustment charge is $0.017 per kilowatt hour. what is the total electricity cost for may?