Can you guys answer question 8 please I’m sure it’s easy

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.  

Using elimination, what is -4x+2y=-12 4x+8y=-24

What is the 17th term in the arithmetic sequence in which a6 is 101 and a9 is 83