Answer
$3\times 7$
Work Step by Step
In general, if $A$ is an $m\times p$ matrix and $B$ is a $p\times n$ matrix, then $AB$ is an $m\times n$ matrix. Here, we are given $m=5$, $p=3$, and $n=7$, so $p\times n$ is $3\times 7$.
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.