Chapter 3 - Graphing Linear Functions - 3.3 - Function Notation - Exercises - Page 125: 17

$x=-2$

The function is $q(x)=\frac{1}{2}x-3$ Substitute $-4$ for $q(x)$ to get $-4=\frac{1}{2}x-3$ Add $3$ to both sides of the equation to get $-4+3=\frac{1}{2}x-3+3$ $\implies -1=\frac{1}{2}x$ Multiply both sides of the equation by $2$. Then, we have $-1(2)=(2)\frac{1}{2}x$ $\implies -2=x$ When $x=-2$, $q(x)=-4$