The ratio of ages of A and B is 4:5. After 6 years, their ages will be in the ratio 6:7. What is the current age of A?

आयु 4x, 5x मान लें। (4x + 6) / (5x + 6) = 6/7। 28x + 42 = 30x + 36 => 2x = 6 => x = 3। A की आयु = 4 * 3 = 12 वर्ष।