Hi Serenafrancis1! :)
The formula for the area of a rectangle is:
[tex]L*W[/tex]
[tex]L=length[/tex]
[tex]W=Width[/tex]
We can input all the information we know to solve for the missing variable:
[tex]L*17=357[/tex]
Divide both sides by 17
[tex](L*17)/17=(357)/17[/tex]
Simplify.
[tex]L=21[/tex]
The rectangle is 21 inches long.
Hope this helps.
-Benjamin
