Answer
$2.25$
Work Step by Step
$E=kW$, thus here $3=k\cdot20$, so $k=0.15$
Thus if $W=15$, then $E=0.15\cdot15=2.25$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.