Atriangle has side lengths of 18 cm , 80 cm, and 81 cm. is this triangle obtuse acute or right. and explain how you got your answer so i can check it

The first week samantha learned to read braille, she could read 10 words per minute. in the second week she increased her speed by 20%. in the third week she increased her speed again by another 25%. how many words could she read per minute by the third week? hurry and tell me!