Answer
r = $\left[\frac{7}{3},4\right]$
Work Step by Step
$8 \leq 3r +1 \leq 13$
1. Separate into two inequalities:
$3r+1 \geq 8$
$3r+1 \leq 13$
2. Solve the inequalities:
$r\geq \frac{7}{3}$
$r \leq 4$
3. Find the intersection to get your answer:
r = $\left[\frac{7}{3},4\right]$
