78/61 cannot be simplified further.
No.
78 simplified is 78.
The GCF of 78 and 130 is 26. 78/26 = 3 130/26 = 5 78/130 = 3/5
78/105 = 26/35
78/91 = 6/7
It is: 78/96 = 13/16 simplified
Yes.
78/100 simplifies to 39/50
It is: 13/78 = 1/6 simplified
It is: 78/126 = 13/21 simplified
12/13