Dan's age is x.
Jack is three years older than Dan, so his age is x+3.
Harold is twice as old as Jack, so his age is 2(x+3).
Harold's age is five times Dan's age.
[tex]2(x+3)=5x \\
2x+6=5x \\
6=5x-2x \\
6=3x \\
\frac{6}{3}=x \\
x=2 \\ \\
x+3=2+3=5[/tex]
Jack is 5 years old.
