Let x be the width of the table. Then the length would be 2x since it is twice as long as the width. The perimeter is found by adding up all the sides of the table: 2x+2x+x+x = 30. Then 6x = 30. x = 5. So the width is 5 feet and the length is 10 feet. Check: 5+5+10+10 = 30.