The simplified expression of
is 
<h3>How to simplify the expression?</h3>
The expression is given as:

Divide 162 and 2 by 2

Take the square root of 81

Apply the quotient rule of indices

Evaluate the difference

Take the square root of x^18

Hence, the simplified expression of
is 
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If you would like to know how many hours will Lena need to work before she can afford to buy the computer, you can calculate this using the following steps:
$900 - $473 = $427
$427 / $7 = 61 hours of yard work
Result: Lena will need to work 61 hours before she can afford to buy the computer.
So if you means 33-55=-22
-22/11=x
so when dividing by a negative, just divide as usual, but just make the answer negative so
-22/11=22/11 times -1/1=2 times -1=-2
the answer is -2