Let the age of father be x years

Let the age of one of his children be y years and age of other children be z years

From given information,

x=2×(y+z)...(1)

After 20 years,

(x+20)=(y+20)+(z+20)...(2)

Substituting value of (1) in (2), we get

2×(y+z) +20=y+z+40

2y+2z−y−z=40−20

y+z=20...(3)

Substituting value of (3) in (1), we get

x=2×(20)

⇒x=40

raat ko m 11 ke baad nhi aa skti behn usse pehle toh thik h or din m bhi thik h agr ho ske toh