They can each be expressed in 180ths. 180 is the LCD (180=9 x 20 and 3 goes into 9, and 2 and 4 go into 20).
90/180, 60/180, 20/180, 45/180, 9/180. All we have to do now is arrange the numerators into order:
9/180, 20/180, 45/180, 60/180, 90/180 which are
1/20, 1/9, 1/4, 1/3, 1/2 in ascending order.