Answer:
46
Step-by-step explanation:
x - age of a son three years ago
3x - age of a father three years ago
x + 3 - age of the son now
3x + 3 - age of the father now
x + 3 + 5 - age of the son in five years time
3x + 3 + 5 - age of the father in five years time
in five years time, the father will be twice as old as his son, so:
3x + 3 + 5 = 2(x + 3 + 5)
3x + 8 = 2x + 16
3x - 2x = 16 - 8
x = 8
x + 3 + 4 - age of the son in four years time
8 + 3 + 4 = 15
3x + 3 + 4 - age of the father in four years time
3×8 + 3 + 4 = 31
the sum of their ages in four years time:
15 + 31 = 46
