Answer:
always
Explanation:
Rearrange the equation to make it easier:
ax+b-b-4=b-b
ax-4=0
ax-4+4=0+4
ax=4
Solve for x by dividing by a:
ax/a=4/a
x=4/a
When it says "a is not equal to 0" it means you can divide by it.
The statement is therefore always.
hope this helps :)