There is no answer to this (for any value of x)
That's because x-x = 0
So x-x-7 is always -7, and never 0
HGW is Wiesler's initals and xx7 was just his number.
Most likely its the serial number
15 percent 0 equals 0; 0 percent 15 equals 0. Both the above are true
yes
maybe
0
0
It equals 0
It equals 0.
0 it equals 0
x=0
For y - 2y - 3y equals 0, y equals 0.