The 7-letter names of these western- & easternmost mainland countries begin with the same letter

b.) plain  

hope this

the one feature that all mediterranean countries have in common is that they border the mediterranean sea.

explanation:

the answer would be the third option, "no, ariel should have added 9^2 and 12^2 and compared that to 15^2."

this is found through the pythagorean theorem, which is a^2 + b^2 = c^2.

this is the correct way of solving the problem:

9^2 + 12^2 = 15^2

81 + 144 = 225

225 = 225