Rub is 7 years older than his brother. Three years ago, the sum of their age is 43. What will be Rub’s age in 12 years’ time?
Let X be Rub's brother's age.
Rub is X + 7 years old.
Three years ago, Rub was X + 7 - 3 = X + 4 years old.
And his brother was X - 3 years old.
The sum of their age three years ago was X + 4 + X - 3 = 43.
2X + 1 = 43.
2X = 42.
X = 21.
Rub is 21 + 7 = <<21+7=28>>28 years old.
In 12 years, Rub will be 28 + 12 = <<28+12=40>>40 years old. Answer: \boxed{40}.