(13x - 11y + 10z) - (-15x + 10y - 15z)

1. Distribute the negative sign: 13x - 11y + 10z + 15x - 10y + 15z.
2. Combine like terms: (13x + 15x) + (-11y - 10y) + (10z + 15z) = 28x - 21y + 25z.