Excuse me, do you want to ask the question "15-x=6"? The equation is solved by the balance method as follows:

1. Subtract 15 from both sides, and the x on both sides of the equation moves to the same side, that is,15-x-15 = 6-15.

2. Simplify it to -x=-9, and remove the negative sign on both sides of the equation, that is, x=9.

The equilibrium method, also known as the two-side equilibrium method of the equation, is a basic method to solve the equation. Based on the identity principle in mathematics, that is, both sides of the equation perform the same operation at the same time, the equation still holds.