Chapter 10 - Exponents and Radicals - Review Exercises: Chapter 10 - Page 693: 11

$f(15)=5$

Substituting $x=15$ in the given function, $ f(x)=\sqrt{x+10} ,$ then \begin{array}{l}\require{cancel} f(x)=\sqrt{x+10} \\\\ f(15)=\sqrt{15+10} \\\\ f(15)=\sqrt{25} \\\\ f(15)=\sqrt{(5)^2} \\\\ f(15)=5 .\end{array}