Answer:
suppose: the age of the man now is x
the sum of the ages of his two sons now is y
(x, y > 0, x, y € N)
so the age of the man 10 years ago is x - 10
the sum of the ages of his 2 sons ten years ago is
y - 20
because now, The age of a man is twice the sum of the ages of his two sons => x = 2y
because Ten years ago, his age was five times
the sum of their ages
=> x - 10 = 5( y - 20)
<=> x - 10 = 5y - 100
<=> 2x - 20 = 10y - 200
<=> 2x = 2y.5 - 180
but x = 2y => 2x = 5x - 180
<=> 3x = 180
<=> x = 60
=> his present age is 60
