Answer:
The given expression is equivalent to -x
That is 
Now Verified that the two expressions are equivalent
Step-by-step explanation:
Given that Genevieve wants to verify that One-fifth (5 x minus 20) minus one-half (4 x minus 8) is equivalent to Negative x
It can be written as below :

Now we can verify the expression is equivalent or not :
Taking LHS

( by using the distributive property )

( adding the like terms )
=RHS
Therefore LHS=RHS
Therefore the given expression is equivalent to -x
That is 
Now Verified that the two expressions are equivalent