What is the rounding or compatible numbers to estimate the sum of 256+321

Little’s law firm has just one lawyer. customers arrive randomly at an average rate of 6 per 8 hour workday. service times have a mean of 50 minutes and a standard deviation of 20 minutes. how long does a customer spend at little’s law firm on average?

Which of the following is correct interpretation of the expression -4+13

The suare root of 9x plus 7 plus the square rot of 2x equall to 7