Answer:

Hope this helped. A brainliest would be very much appreciated. (I need 4 brainliest so I can level up) :)
Complementary I’m sure but I could be wrong
perimeter =48
18+18+6+6=48
x-12=x/3
Multiply both sides by 3
3x-36=x
3x=x+36
2x=36
x=18
18-12=18/3
6=6
One side 18 another side 6
<h3>
Answer: 112.5 square units</h3>
Work Shown:
A = area of the triangle
A = base*height/2
A = 9*7/2 = 63/2 = 31.5 ... see note1 below
B = area of rectangle
B = base*height
B = 9*3 = 27
C = area of parallelogram
C = base*height .... see note2 below
C = 9*6 = 54
If you're confused where I got the 6 from, check out the attached image below.
D = total area of the composite figure
D = A+B+C
D = 31.5 + 27 + 54
D = 112.5
-------------------------
note1: The vertical component of the triangle is 9 units because this is part of the rectangle. The rectangle has opposite sides that are the same length. The parallelogram's vertical sides are 9 units long as shown by the single tickmark.
note2: a rectangle is essentially a special case of a parallelogram. In other words, a rectangle is a parallelogram with 4 right angles. So this is why the formula "area = base*height" shows up identical for both rectangles and parallelograms. Keep in mind that the height is always perpendicular to the base. You will not use the segments marked with double tickmarks.