Answer:
First let's work out the lengths of each side using the equation
(y2-y1)²+(x2-x1)² and then find the square root of your answer
We get BC as root of 26
AB as root of 113
AC as root of 85
To get the perimeter of the triangle add up the values
root of 85+root of 113+root of 26=24.95 (use the unit specified)
I know the answer is a bit rushed but if you do have any questions let me know
