Chapter 7 - Functions and Graphs - 7.2 Domain and Range - 7.2 Exercise Set - Page 459: 56

$a.\quad-5$ $b.\quad 0$ $c.\quad 18$

$a.\quad $ $x=0$ belongs to the interval $x\leq 5$, so we calculate its function value with $f(x)=x-5$ $f(0)=0-5=-5$ $b.\quad $ $x=5$ belongs to the interval $x\leq 5$, so we calculate its function value with $f(x)=x-5$ $f(5)=5-5=0$ $c.\quad $ $x=6$ belongs to the interval $x\gt 5$, so we calculate its function value with $f(x)=3x$ $f(6)=3(6)=18$ $a.\quad-5$ $b.\quad 0$ $c.\quad 18$