No.
The only common factor of 19 and 51 is 1.
51/48 = 3/4
0.255 simplified is 51/200
20.4 percent as a simplified fraction = 204/1000 = 51/250
115/255 can be simplified to 23/51
9/51 = 3/17
1.8 as a simplified fraction = 18/10 = 9/5 = 1 and 4/51 and 4/5
It is already simplified and in its lowest terms as -51/70
51 and 40 are coprime so the ratio 51/40 cannot be simplified.
0.408 = 408/1000 = 51/125
No.
It is: 30/51 = 10/17
51/100 cannot be simplified further.