To solve for these, we will use formulas and convertions as we go.
For 1:
We are looking for kg (kilograms) to g (grams). 1 g = 0.001 kg.
We have 2.5 kg. This means we must multiply 2.5 by 1,000.
2.5 x 1,000 = 2,500.
1.) is 2,500 grams.
For 2:
This problem has multiple steps, but we will successfully solve it. As of now, we have yards. There are 3 feet in a yard, and 12 inches in 1 ft. We will convert yards to feet, and then feet to inches.
500x3 = 1500, 1500 x 12 = 18,000.
2.) is 18,000 inches.
For 3:
There are 2,000 pounds in 1 ton. Using this, we can determine how many tons we have.
7,000/2,000 = 3.5
3.) is 3.5 tons.
I hope this helps!
Because this is a positive parabola, it opens upwards, like a cup, and the vertex dictates what the minimum value of the function is. In order to determine the vertex, I recommend completing the square. Do that by first setting the function equal to 0 and then moving the 9 to the other side by subtraction. So far:

. Now, to complete the square, take half the linear term, square it, and add that number to both sides. Our linear term is 6. Half of 6 is 3 and 3 squared is 9. So add 9 to both sides.

. The right side reduces to 0, and the left side simplifies to the perfect square binomial we created while completing this process.

. Move the 0 back over and the vertex is clear now. It is (-3, 0). Therefore, 0 is the minimum point on your graph. The first choice above is the one you want.
This is really a long way to go to make something complicated
out of something simple. The last choice does the job.
cos(180) = -1
sin(180) = 0
So 4 [cos(180) + i sin(180) ]
= 4 [ -1 + i (0) ]
= -4 yay!
Just multiply the two, your answer should be 21.06