How do you find the area of a triangle whose vertices have the coordinates ( -1 -1) (-13) and (5 -1)?

If you mean vertices of: (-1, -1) (-1, 3) and (5, -1) then when plotted on the Cartesian plane it will form a right angle triangle with a base of 6 units and a height of 4 units.

Area of triangle: 0.5*6*4 = 12 square units