No, it cannot.
yes
6/19
Expressed as a proper fraction in its simplest form, by dividing the numerator and denominator by 2, 42/76 = 21/38 or twenty-one thirty-eighths.
13/21 can't be reduced.
Yes. 76 and 154 are both divisible by 2: 76/154 = 38/77
21/40 cannot be reduced.
25/21 is already reduced to its lowest terms
76/84 = 19/21
The fraction 19/21 cannot be reduced any more.
736 and 21 are comprime so the fraction cannot be reduced.
No.
Yes, 21/3 = 7/1