Answer :
The perimeter is going to be 2x+2y=222 (x being length and y being height.)
We know our length, x, so plug it in.
2(60)+2y=222
120+2y=222
Subtract.
2y=102
Divide.
y=51
Your width is 51mm.
We know our length, x, so plug it in.
2(60)+2y=222
120+2y=222
Subtract.
2y=102
Divide.
y=51
Your width is 51mm.
Perimeter is when you add all of the sides together. To solve this problem, you would double 60 because their are 2 sides of the length. Then you would subtract 222 and 120 to get 102. Then you would divide that by 2 to get 51mm as the answer for the width.