Aseamstress is making a decorative pillow and wants to see lace around the trim. the pillow is in the shape of a triangle with vertice (7,7)(10,3)(7,3). how many inches of lace will she need if each unit on the grid is one inch?

I think it will be 8 1/3 inches. 
(7,7) and (7,3) are 4 units apart
    7-3  = 4
    7-7  = 0
(7,3) and (10,3) are 3 units away
  3-3 = 0; 10-7 = 3
(7,7) and (10,3) are 4/3 units away or 1 and 1/3
  7-3 =  4 
 7-10 =-3
  Then, take the absolute value because you can't have negative inches of lace, you get 4/3 or 1 1/3. 
Add them all together for perimiter: 
 4+3+1 1/3 = 8 1/3 inches of lace

Hope this helps!