Each time elena buys lunch at school, the balance on her school lunch account changes
by -$3. last month, elena's balance changed by -$36 in all. she wants to know how
many times she bought lunch last month.

Find the difference (8ab+a+2) - (3ab+6)

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?

Molly shared a spool of ribbon with 12 people. each person received 3 feet of ribbon. which equation can she use to find r, the number of feet of ribbon that her spool originally had?