Answer:
The unknown dimension is 35
Step-by-step explanation:
The perimeter of a rectangle is l+l+w+w or 2l+2w (l=length, w=width)
[tex]l+l+w+w=84[/tex]
[tex]7+7+w+w=84[/tex]
[tex]14+w+w=84[/tex]
then we subtract 14 from 84
[tex]w+w=70[/tex]
[tex]2w=70[/tex]
[tex]\frac{70}{2}=35[/tex]
[tex]w=35[/tex]
Let's check our answer
[tex]35+35+7+7=84[/tex]
Hope this helps :-)
