This is one of the easiest questions in this paper and could be solved mentally, check below –

Out of 120 persons, 80 are Indians and 40 are foreigners. – (i)
Out of 120 persons, 70 can speak English, and 50 cannot speak English. – (ii)

To maximise Indians who can speak English, we can assume all can speak English but the maximum possible number of Indians who can speak English is 70 because (ii) clearly states that only 70 can speak English. Hence, all the 70 English-speaking people are Indians.

To minimise number of Indians who can speak English, we assume all 40 Foreigners can speak English. Now, only 30 Indians (total 70 – 40 Foreigners) can speak English.

So, English-speaking Indians will be between 30 to 70