The formula is this: (Userlevel - Target level + 30)%
Since both are 100 lvl, formula,
100 - 100 + 30 = 30%
Now factoring in the evasion and accuracy,
P = Abase x Accuracy/Evasion
P is the probability of the move hitting
Abase is the base accuracy of the move. In this case, it is 30.
Accuracy is the amount from which the boosts the user has acquired.
Evasion is the amount from which the boost the target has acquired.
After doing the calculation, the final answer comes to 3.33%
Hope I helped!