How many different arrangements can be made with the letter of the word 'm o r o c c o'?

Since the order matters, it's a permutation of 7 letters, but mind you in 
MOROCCO. you have 3 O's and 2 C's, Hence the arrangements are:

⁷P₇ /(3!2!) = 7!/(3!2!) = 5040/(3!2!) = 420 arrangements 

Okay so for every triangle has three angles that always add up to 180 degrees. and to tell the difference between whether they are secure, right or obtuse is that acute: has one angle that is less than 90 degrees. right triangle means there is at least one angle that is exactly 90 degrees. and an obtuse angle has an angle that is bigger than 180 degrees. i’ll do #13 as an example: 13. 40 and 50 so if every triangle has 180 degrees 40+50= 90 degrees then180-90= 90 degrees so the third angle is 90 degrees and because this triangle has a 90 degree angle it means it is a right triangle