Distances are considered to be non-negative in all cases.
The absolute value function is necessary to get a positive result when the difference of coordinate values is negative.
The square root function is defined to return a positive result always, so no absolute value function is required when the distance is found using the square root function.
The answer is the third one. which is:
He made a computation error when he added 10.35+7.6
I believe <span>2 3 5 7 11 13 17 19 23 29 31</span>
Answer:

Step-by-step explanation:
Let's re-write the equations in order to get the variables as separated in independent terms as possible \:
First equation:

Second equation:

Third equation:

Now let's subtract term by term the reduced equation 3 from the reduced equation 1 in order to eliminate the term that contains "y":

Combine this last expression term by term with the reduced equation 2, and solve for "x" :

Now we use this value for "x" back in equation 1 to solve for "y":

And finally we solve for the third unknown "z":
