The Length Of A Rectangle Is Fixed At 30cm. What Widths Will Make The Perimeter Greater Than 100cm?

2 x 30 + 2 x W > 100
     60 + 2 x W > 100
  2 x W > 100 - 60
  2 x W > 40
  W > 40/2
  W > 20
Check:
2 x 30 + 2 x 21 > 100
  60 + 42 > 100
  102 > 100