Answer:
[tex]d=-5 \text{ or } d=5[/tex]
Step-by-step explanation:
[tex]|-3d|=15\\\\-3d=15 \text{ or } -3d=15\\\\\frac{-3d=15 \text{ or } -3d=15}{-3}\\\\\boxed{d=-5 \text{ or } d=5}[/tex]
Hope this helps.