How do I work this problem?

(40 points) i need some . an answer definition is appreciated as well.

Find the perimeter of the triangle with vertices  d(3, 4),  e(8, 7), and  f(5, 9). do not round before calculating the perimeter. after calculating the perimeter, round your answer to the nearest tenth.  

Jenny earned a 77 on her most recent test jenny score is no less then 5 points greater then 4/5 of terrance’s score if t represents terrance score which inequality represents the situation