Answer
$$6-8x.$$
Work Step by Step
We have
$$(7-3x) - (5x+1)=7-3x-5x-1=6-8x.$$
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.