Most coins we deal with on an everyday basis are called fair coins. Because there is a 50-50 chance of getting a head or tail. Now, you are an evil genius and you have made an unfair coin. Say it has a 75% chance of giving you a Head. So, if you toss the coin 4 times, on average, you get 3 Heads. Because there is a 75% chance of getting a Head, there is a 25% chance of getting a Tail. Let us represent such a coin by $$C = \frac{75}{100} \times H + \frac{25}{100}\times T$$. Here, the $$\frac{75}{100}$$ represents the probability of getting a Head (H), etc.
What is the probability of getting a tail if $$C = \frac{30}{100} \times H + \frac{70}{100}\times T$$