What is the mean median range mode for 31 28 30 31?

To work out the mean you add them all up and divide by how many numbers there are:
31+ 28 + 30 + 31 = 120 
120 / 4 = 30

to work out the median you order the  numbers and then find the middle value
28 30 31 31
therefore the median is 30.5

to find the mode you look for the most common number
which is 31

hope this helps you

One unique triangle, because those angles add up to 180, and that's how many degrees there are in one triangle.