Hi pls help me huryyy pls i have 5 min

In simplified exponential notation, the expression a^2•a^-3•a 1/a 0

What is the value of the expression 9+n/3-6 when n = 12? 1. 5. 7. 12.

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?