50/91 is already simplified.
12 over 91 can't be simplified.
It is: 91/119 = 13/17 simplified
No; it is 1/7 simplified.
Since 91 and 9 don't have any common multiples, 9/91 cannot be simplified.
It is: 91/70 = 13/10 simplified
78/91 = 6/7
Yes.
38 over 50 simplified = 19/25
No. It can be further simplified to 4/7
3/13
7/13
Already simplified!