She made the mistake of grouping unlike terms and factorizing.
Given that
Helene is finding the sum (9 + 10i) + (–8 + 11i).
She rewrites the sum as (–8 + 11)i + (9 + 10)i.
We have to determine
Which statement explains the property of addition that she made an error in using?
According to the question
The mistake she did is in the second term distributing.
(9+10i) is not equal to (9+10)i
Similarly (-8+11i) is not equal to (-8+11)i.
The correct method she should have done is given below;
Grouping real terms together and imaginary terms together and finding the sum is,

Hence, she made the mistake of grouping unlike terms and factorizing.
To know more about Complex Number click the link given below.
brainly.com/question/10078818
Answer:
The median, because the data distribution is skewed to the right
Step-by-step explanation:
If the longer part of the box is to the right (or above) the median, the data is said to be skewed right. If the longer part is to the left (or below) the median, the data is skewed left. The data is skewed right. The median would be a better estimate, because one or two numbers on the high end will cause the numbers to be skewed to the right, and the mean to be high
The sum of two numbers
5.036.
first number: one number has 4 in the tenths place, 7 in the thousandths
place.
=> x.4x7
2nd number: 1 in ones place and 2 in the hundredths place.
=> 1.x2x
Now, we have the 2 numbers with given clues:
=> x.4x7 + 1.x2x, where x is the missing number.
Note that in adding numbers, we start from the right most.
=>x.4x7 + 1.x2x = 5.036
=> x.4x7 + 1.x29
=> x.407 + 1.x29
=> x.407 + 1.629
=> 3.407 + 1.629
=> 5.036
The expressions is undefined in the set of the real numbers.