Math question/help/please-

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

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

Suppose that prices of a gallon of milk at various stores in one town have a mean of $3.71 with a standard deviation of $0.10. using chebyshev's theorem, what is the minimum percentage of stores that sell a gallon of milk for between $3.41 and $4.01? round your answer to one decimal place.