The theoretical probability of getting heads is 50%. 50% of 50 is 25. So, 20 % more than 50% is 20% * 25 + 25 = 5 + 25 = 30. That means that the coin should show 30 heads fo have an experimental probability of 20% more than the theoretical probability. You can check that 30 out of 50 is 0.6. Which is 0.1 more than 0.5. And 0.1 is 20% of 0.5. Then 0.6 is 20% more than 0.5.
