If the ratio of the ages of A and B is 3:5 and the sum of their ages is 80 years, what is the age of B?

मान लीजिए आयु 3x और 5x है। 3x + 5x = 80 => 8x = 80 => x = 10। B की आयु = 5x = 5 * 10 = 50 वर्ष।