Can anyone with this? (ignore question b)

-- ' Y ' plus ' Z ' must be equal to ' X ' .

-- A more elegant statement:   

           (The sum of everything flowing into the junction)
is equal to
           (the sum of everything flowing out of the junction).

-- An even more elegant statement:

If water flowing into the junction is positive and
water flowing out of the junction is negative, then

     (The sum of all flow at the junction)  =  Zero.

The reason for all of these statements is the Law of Conservation of Water:

                   Water can't be created or destroyed.

If there are no faucets or leaks at the junction, then the flow in and
the flow out are equal.

What sports are they giving you

Apossible long term health effects of stress would be work