Hey guys, I just need some quick help! Can anyone explain to me how to find the square root of this number... or pretty much any other number in general?

Like, I know for a fact that this is 4. But my teacher stated that I cannot find the square root of a negative number. This, for some reason, turns to a POSITIVE 4 and I just do not understand why. Can you guys, like, you know, explain?

The box plots show the distributions of the numbers of words per line in an essay printed in two different fonts.which measure of center would be best to compare the data sets? the median is the best measure because both distributions are left-skewed.the mean is the best measure because both distributions are left-skewed.the median is the best measure because both distributions are symmetric.the mean is the best measure because both distributions are symmetric