You need more information to answer this question. Is there a table or percentage for that age group?
Answer:
13.6 inches
Step-by-step explanation:
We can use Pythagorean theorem: 
Let c be the diagonal length, a for length, and b for width.
Substitute the values.

c=13.6 inches
Answer:
Isolate the variable by dividing each side by factors that don't contain the variable. Inequality Form:
<h2>
n < -1</h2>