Sum of present age of A, B, C and D is 76 years. After 7 years ratio of their ages is 7 : 6 : 5 : 8. What is C’s present age.

At present sum of age = 76

After 7 years sum of age will be

7x + 6x+ 5x+ 8x = 76 + 7 × 4

26x = 76 + 28

????= $frac{{104}}{{26}}$

x = 4

C’s present age = 5x – 7

= 20 – 7 = 13