Area is 2 dimensional while volume is three dimensional.
It is 16,000. because 0 is lower than 5
So, you want to do the operations on both sides.
5/4 (x-5)=-6 becomes
x-5= -6/(5/4)
becomes
x= -6/(5/4)+5
and x=0.2
Hope this helped!
See image below it keeps going