The missing number is 16
<em><u>Solution:</u></em>
Given that mean of data is 18
Let "x" be the missing number
The data set is:
21, 11, x , 27, 22, 13, 16
Sum of data set = 21 + 11 + x + 27 + 22 + 13 + 16
Sum of data set = 110 + x
<em><u>The mean is given by formula:</u></em>

Substituting the values we get,

Thus the missing number is 16
In this question, it is given that
Walter wants computer software that cost $129. He has $57 saved.
he saves a maximum of $15 a week, the following inequality can be used to find how many weeks it will take Walter to save enough money to buy the software.

And we have to solve this inequality for x.
First we subtract 57 to both sides. And on doing so , we will get

Dividing both sides by 15.
\
Correct option is A.
11/20=0.55
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Hoped it helped</span>
I think the answer is C
Hope it helps