Beta emission occurs when a nucleus has an excess of protons (for radiation) or neutrons (for radiation). Potassium-40 is a well-known one to decay via radiation.
If this is a GCSE question, this distinction is not required.
For beta(-), the Isotope caesium 137 decays into barium 137. Number of protons increases from 55 to 56.
For beta(+), sodium 22 decays into neon 22. Number of protons decreases from 11 to 10.