Problem Solving (PS) | Re: Triangle ABC is symmetric about the y-axis. Point A is located at (-4,

one co-ordinate of the triangle is (4,0) so the horizontally opposite co-ordinate is (4,0) as the triangle is symmetrical about y-axis.
length of this line of triangle is 4-(-4) = 8.
as the perimeter is 18, sum of remaining two sides = 10 and so the length of each side is 5
if we consider half part of the triangle, it is a right angled triangle with hypotenuse = 5, base = 4 making height = 3

so it is a triangle with height = 3 and base = 8, hence area = 1/2 * 8 * 3 = 12 ... option D

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