The correct answer is option 2.
3 = 0
x - a = 0
x = a
x + b = 0
x = -b
We do not multiply any of these values by 3 because in a way, 3 is acting as another "zero" of the equation. Though, as shown above, it does not equal 0, it still does not apply to any of the other equations solved above.
Hope this helps!! :)
