Solution to 3.
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| T | T | T | F | F | T | T |
| T | T | F | T | F | F | T |
| T | F | T | F | T | T | F |
| T | F | F | T | T | T | F |
| F | T | T | F | F | T | T |
| F | T | F | T | F | F | T |
| F | F | T | F | T | T | T |
| F | F | F | T | T | T | T |
The argument is valid, since there is no row in which all the premises (in bold) are T and the conclusion (italic) is F.