Answer
$n=3$
Work Step by Step
Since the quadrilaterals are similar, the corresponding sides will be proportional. So, set up a proportion...
$\frac{AB}{HJ}=\frac{BC}{JK}$
Substitute in the appropriate values...
$\frac{5}{10}=\frac{n}{n+3}$
Cross multiply...
$5(n+3)=10(n)$
Distribute the five...
$5n+15=10n$
Subtract $5n$ from both sides...
$15=5n$
Divide by five...
$n=3$
