We use letters to substitute for unknown numbers. I hope this helps. :)
I took the test, it is <span>c. An increase in n, the number of payment periods, will create a decrease in P, the monthly payment.</span>
ANSWER

EXPLANATION
The surface area of a triangular prism is
equal to the area of two triangular faces
plus the area of the three rectangular faces.
The area of the equilateral triangle is calculated using the formula:

where s=6 is the length of one side.
and b=6 is the breadth of the rectangle and h=10 is the height of the rectangle.
Surface area


=211.2square inches.
If you mean proof that the opposite sides of a parallelogram are equal, you draw a diagonal then prove that the 2 triangles formed are congruent.
Answer:
Area or parallelogram = base * height
Area = 9 units * 2/3 units
Area = 9/1 * 2/3 square units
Area = 18/3 square units
Area = 6 square units
Answer: area = 6 square units