For the answer to the question above,
A - C = ( -2, 9) - (- 2 -3)
= ( 0, 12)
AC = 12
B - C = (7 - 3) - ( - 2 -3)
= (9, 0)
BC = 9
ABC is a right -angled triangle with AC as the hypotenuse
AC = sqrt( 9^2 + 12^2)
= sqrt(81 + 144)
= srqt(225)
= 15
Perimeter = 12 + 9 + 15
= 36 units
So the answer is 36 units
I hope my answer helped you.