So, 30 is the perimeter. We are told the table is twice as long as it is wide.
So, we have think of 2 numbers, one being twice as big than the other. So, it is a rectangle The two number represents the length and the width. To find the perimeter we add all the lengths and the widths. Since the pool table is a rectangle we have two lengths and two widths.
So,
the tow numbers be 10 and 5. 5 is half of 10 and, when multiplied by 2 it is 10. So just to make sure the numbers 5 and 10 work out lets do a calculation.
So,
10+5+10+5 = 30feet. This proves that the sides are these two numbers.