How many diagonals does a 12-sided convex polygon have? What is the general rule for a convex polygon with n sides?

Cynthia takes her dog to the park every 2 days. she bathes her dog every 7 days. if she took her dog to the park and bathed him today, how long will it be until she does both on the same day again?

/is used for a fraction 1) if x = 2/3 and y = 3/4, what is the value of (x + y) (x/y) expressed as a common fraction? 2) what is the least positive integer greater than 1 that leaves a remainder of 1 when divided by each of 2, 3, 4, 5, 6, 7, 8, and 9? 3) the ponde family's powerjet pumps 420 gallons of water per hour. at this rate, how many gallons of water will it pump in 45 minutes? 4) kim's insurance company pays 80% of the cost of all prescription medication she purchases in a year beyond the first $250 worth of prescriptions. her prescriptions for this year cost a total of $570. how many dollars of this amounts will kim's insurance company pay?

Which best explains why this triangle is or is not a right triangle?