Question 150322
(8 – 8)(7 – p) = 0

This is an identity.  Check it out:


(8-8)=0
(7-p)=(7-p)


Plug in these values into (8-8)(7-p)=0
(0)(7-p)=0


This is saying "zero times a quantity equals zero".  This is always true, no matter what the quantity is, which makes this an identity.