The answer for your question is 45 cm long
The perimeter of a triangle is the sum of its side lengths.
The perimeter of the triangle is: 
<u>The sides of the triangle are:</u>
Side 1 = (8d - 3) cm
Side 2 = (6d + 2) cm
Side 3 = (7f + 8) cm
The perimeter (P) is calculated as:
P = Side 1 + Side 2 + Side 3
So, we have:

Remove brackets

Collect like terms


Hence, the perimeter of the triangle is: 
Read more about perimeters at:
brainly.com/question/6465134
Answer:
-55
Step-by-step explanation:
This question is nasty. It sounds like you should be finding area of the figure you see. I'll do that first, although I don't think it's the right answer. (But it might be).
Area Trapezoid = (b1 + b2) * h / 2
b1 = 8
b2 = 12
h = 5
Area Trapezoid = (8 + 12 ) * 5 / 2
Area Trapezoid = 20 * 5/2
Area = 50 square feet.
The problem is that no lumber yard will cut that for you without charging you. The practical answer is 12 * 5 = 60 square feet is what you will have to buy. Then you cut out the triangles for yourself.