Yes! Now I am in 10th

Let's try to find the maximum number of marks one can get and not be promoted.

One can get at most $9$ marks from the first exam to not pass it and thus if one fails the first exam, the maximum number of total marks is $9 + 70 = 79$ .

One can get at most $22$ marks from the second exam to not pass it and thus if one fails the second exam, the maximum number of total marks is $30 + 22 = 52$ .

Hence, the maximum number of marks one can get and not be promoted is $79$ , which means that the answer is $\boxed{80}$ , since with $80$ marks, promotion is quaranteed.

80 is the lowest score (combined) All other scores can be achieved in the second exam(full) and so there wud be very less marks scored in the first one(below 10)

For any score less than 70, all marks could have come from just the second exam. In order to see that both exams have been passed, we need at least 10 more marks that have no option except to come from the other test. Thus, we need at least 80 to know both tests had enough marks to pass.