Question

Jack's height is half of his father's height. If the sum of their heights is equal to 9 feet, then Jacky's height(in feet) is .

Answer 1

Let Jack's height be $x$ feet.
Accordingly, his father's height would be $2x$ feet.
Given that the sum of their heights is $9$ feet
$\Rightarrow x+2x=9$
$\Rightarrow 3x=9$
$\Rightarrow x=3$ feet
Jack's height is $3$ feet.