Given :
The perimeter of the rectangle = p = 222 mm
And the length of the rectangle = l = 60 mm
Let the width = w
The perimeter of the rectangle = p = 2 ( l + w )
so,
[tex]\begin{gathered} p=2\cdot(l+w) \\ 222=2(60+w) \end{gathered}[/tex]solve the equation to find w:
[tex]\begin{gathered} \frac{222}{2}=60+w \\ 111=60+w \\ 111-60=w \\ \\ w=51 \end{gathered}[/tex]The answer is : the width of the rectangle = 51 mm