Explanation:
Let;
perimeter = 420cm
L = length
w = width
perimeter of rectangle = 2l +2w
420= 2l + 2w
but;
width = L - 30cm ( 30 cm less than length)
420cm = 2L + 2( L - 30cm)
420cm = 2L + 2L -60cm
420cm + 60cm = 2L + 2 L
480 Cm = 4L
L = 480cm ÷ 4
L = 120 cm
therefore, the length is 120 cm and width,
(L - 30cm)
= 120cm - 30cm
= 90cm
Therefore the width is also 90cm