Explanation:

Total age of brother and sister = 26 × 2 = 52
After 4 years the total of their age
52 + 4 + 4 = 7x + 8x
15x = 60
x = 4
After 4 years brother's age = 28 years
sister's age = 32 yeras
Brother's present age = 28 – 4 = 24 years