200 persons have a skin disease, our of which 120 presons are effected with chemical `C_(1)`, 50 with chemical `C_(2)` and 30 with chemical `C_(1) and C_(2)` both. Find the number of persons who
(i) are effected with `C_(1) or C_(2)`
(ii) are effected with `C_(1)` but not `C_(2)`
(iii) are effected with `C_(2)` but not `C_(1)`.

Explanation

Here `n(C_(1))=120,n(C_(2))=50,n(C_(1)capC_(2))=30and n(U)=200`
(i) `n(C_(1)cupC_(2))=n(C_(1))+n(C_(2))-n(C_(1)capC_(2))`
`=120+50-30=140`
(ii) `n(C_(1)-C_(1))=n(C_(1))-n(C_(1)capC_(2))`
`=120-30=90`
(iii) `n(C_(2)-C_(1))=n(C_(2))-n(C_(1) cap C_(2))`
`= 50 - 30 = 20`.