1. **Problem statement:** We are given the number of students enrolled in commerce only, mathematics only, both commerce and mathematics, and others. We need to find the total number of students enrolled either for commerce or mathematics. 2. **Given data:** - Commerce only = 20 - Mathematics only = 90 - Both commerce and mathematics = 30 - Others = 60 3. **Formula used:** The total number of students enrolled in commerce or mathematics is given by the union of two sets: $$\text{Total} = \text{Commerce only} + \text{Mathematics only} + \text{Both}$$ 4. **Calculation:** $$\text{Total} = 20 + 90 + 30 = 140$$ 5. **Explanation:** We add the students enrolled only in commerce, only in mathematics, and those enrolled in both to avoid double counting. The students enrolled in others are not included as they are not part of commerce or mathematics. **Final answer:** $$\boxed{140}$$