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

Use the distance formula in order to find the length of each side of the triangle. 

>(7, 7) & (10, 3)
√[(7-10)² + (7-3)²] = 5

>(10, 3) & (7, 3)
√[(10-7)² + (3-3)²] = 3

>(7, 7) & (7, 3)
√[(7-7)² + (7-3)²] = 4

Adding all lengths (or solving for perimeter), we have: 5 + 3 + 4 = 12 

The seamstress will need 12 inches of lace.