If used compensation to find product of 37x4 first she found 40x4=160 then adjusted that product by adding 3 groups of 4 to get her final answer 172. what did she do incorrectly?

How do i do this activity, is appreciated

Ann and betty together have $60 ann has $9 more than twice betty’s amount how much money dose each have

Weekly wages at a certain factory are normally distributed with a mean of $400 and a standard deviation of $50. find the probability that a worker selected at random makes between $450 and $500