The ratio of ages of A and B, four years ago, was 3 : 4 . 6 years from now, the ratio of the ages of A and B will be 7 : 9 . What is the sum of their present age?

148 years

4 years ago ⇒ A : B = 3 : 4

⇒ \(\frac{3x + 10 }{4x + 10}\) = \(\frac{7}{9}\)

⇒ 27x + 90 = 28x + 70

⇒ x = 20

4 years ago age of A and B = (3 x 20), (4 x 20) = 60 , 80

Now, Present age of A and B = (60 + 4), (80 + 4) = 64 , 84

Sum = 64 + 84 = 148 years