a}130/200=.................=......................... 90/500=.......................=.............................
63/300=...................=........................
b}1/4=.....................=......................... 2/5=...........................=..........................
10/25=.....................=.......................
130/200=65/100=13/20
63/300=21/100
1/4=1/4
10/25=2/5
90/500=-9/50
2/5=2/5