We have the next formula for the perimeter of a rectangle
[tex]P=2l+2w[/tex]where l is the length and w is the width
in our case
P=24m
l=8m
w=?
we substitute the values
[tex]24=2(8)+2w[/tex]we simplify the expression
[tex]24=16+2w[/tex]then we isolate the w
[tex]\begin{gathered} 2w=24-16 \\ 2w=8 \\ w=\frac{8}{2} \\ w=4 \end{gathered}[/tex]The width is 4 m