It's difficult to read your question. I assume that you want to balance an equation like this:
The main things to remember are:
- The sum of the subscripts must be the same on each side of the equation.
- The sum of the superscripts must be the same on each side of the equation.
Identify the particle
What particle has a charge of -1 and a mass near zero? An electron (or beta particle)!
The complete equation becomes