Answer:
A) The coordinates of the fourth vertex are:
1) x-coordinate:

2) y-coordinate:

B) The point of intersection of the diagonals is: 
Step-by-step explanation:
We need to remember that the diagonals of a parallelogram intersect each other at a half-way point and the midpoint of each diagonal is the same.
The midpoint formula is:

Since:

We can find the coordinates of the fourth vertex
through these procedure:
1) x-coordinate:

2) y-coordinate:

Therefore, fourth vertex is
Since the point of intersection of the diagonals is the midpoint of a diagonal (Remember that
), this is:

Therefore, the point of intersection of the diagonals is 
8+2x
x standing for Julie's age
N-1(-1/2) is the formula because the sequence is taking half of the previous number and changing its sign
Because the balls or spheres are tightly packed in a cube, their radius is approximately equal to 2 ft. The volume of a sphere is calculated through the equation,
V = 4/3πr³
Substituting the known radius,
V = 4/3π(2 ft)³
V = 33.51 ft³
The 9 spheres will have a total volume of 301/59 ft³ which is also equal to 521152.52 in³.