Which of the following equations is equivalent to 2/3x - 1/2y = 6? 2x - y = 6 2x - y = 36 4x - 3y = 36

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?