Urgent! test tomorrow! need factoring with steps or explanantion. i don't understand how you get the gcf when you have a number in front of the x^2

Quadrilateral efgh was dilated with the origin as the center of dilation to create quadrilateral e'f'g'h'. the quadrilateral was dilated using a scale factor of 2.5. the lengths of the sides of quadrilateral efgh are given. what is the length of side f'g'?