5/4x+7/12x is the same as 15/12x+7/12x = 21/12x
true
You add the numerators and put over the denominator.
You subtract the numerators, and place it over the common denominator.
If you mean to continue the pattern indefinitely, adding more digits, and one more "1" in every cycle, then it is NOT rational. In the case of a rational number, the EXACT SAME group of digits has to repeat over and over (perhaps after some other, initial, digits), for example:0.45113113113113113... Here, the group of digits "113" repeats over and over, so the number is rational.
the fraction is percent over 100 and fraction over the whole. Whatever number is missing you multiply across in an X with the end being the empty space.
All numbers with a finite number of decimal digits are rational. Some that infinitely many decimal digits are rational as well. If you mean to repeat the pattern, adding one more "1" every time, then no, it is not rational - rational numbers repeat the SAME sequence of digits over and over (for example, 0.1515151515...), at least eventually (they may start with some digits that are not part of the repeating part, such as 3.87112112112...).
is 5 over 7 a rational number
It is rational
It is rational
Rational.
Rational.
If it ends there, it is rational. If it continues with the same digit (2 in this case) over and over, it is also rational.