Hey there I just saw no one answered this problem and I know this is a little late but I will answer it anyways.
Answer: The answer to this problem would be points A and B
You add/subtract complex numbers simply by adding/subtracting real parts and imaginary parts.
So, the real part of this sum is the sum of the real parts:

And the imaginary part of this sum is the sum of the imaginary parts:

So, you have

Answer:
7+27i
Step-by-step explanation:
(18+4i)+(-11+23i)
=18+4i-11+23i
=7+27i
Answer + Step-by-step explanation:
(a)
Check the attached image.
(b)
Range of sample means : 7.5 - 5.75 = 1.25
(c)
The closer the range of the sample means is to 0 ,
the more confident they can be in their estimate . 
The farther the range of the sample means is from 0 ,
the more confident they can be in their estimate .
The mean of the sample means will tend to be a better estimate
than a single sample mean . 
A single sample mean will tend to be a better estimate
than the mean of the sample means .