Name the intersection of AD and DF

What's the difference between: x≥0 and nonnegative integer. ?

Find the indicated value, where g(t) = t^2-t and f(x)= 1+x a. -2 b. 0 c. 2 d. 8

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?