I Animal one time this year, fell out with the hunt for recipes.
A guarantee with % no longer hope and not looking. Just decide something like that.
Percentage of the probability of a certain subject is laid on one particular puzzle, as I understand it, not on the number of solved one promised subject. All very unpredictable, and as correctly noted by
@Vovka, to increase the likelihood of without a booster will not do.
Decide quite a lot, about once in three months, even without any boosters, one artifact falls out.
good Luck!