1 in 14 or 1/14
this is the formula I used to calculate:
Probability = Favorable cases / Possible cases
1, 3, 5, 7, 9 are the possible digits
meaning you have 5! possible combinations or 120 combinations
Only problem is with the simplifying.
We all know that 5/5 = 1, it is natural to assume (x+a)/(x+a) is also 1, but in some cases where x+a=0, it is undefined. In this equation, where they simplify (x-2) and (x-6), you must say that x is not 2 nor 6 or, you just delete 0/0 which is undefined.
Therefore the only solution would be x=-1
There are 7 tens, so i want to say 10^7
10 to the seventh power
