The number of diagonals in a certain regular polygon is equal to two times the number of sides. How many sides does this polygon have?
The formula for the number of diagonals in a polygon is \(s(s-3) \div 2\), where s is the numberof sides.
Setting this equal to 2s, we have: \({s(s-3) \over 2} = 2s\)
Solving, we find s = 0 or 7.
But, s can't be 0, so \(s = \color{brown}\boxed{7}\)