Given N , what is mABC

Find the solution of this system of equation -7x+y=-20 9x-3y=36

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%

Find the maximum value of p= 4x + 5y subject to the following constraints :