Tina is 7 years younger than her cousin, Sierra. Their ages add up to 31. How old is Tina?

What are “like terms”? why can we only add like terms?

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?

Pranza plotted point a in the coordinate plane below.