Verbal | HELPER VERBS - REPLACING MAIN + HELPER VERBS IN SAME TENSE

Dear Experts and fellow members,

Hi.

I am facing some trouble with helper verbs, commission of verbs and their tenses.

I'll try to clear my doubts by using some examples:

1. I walk faster than Mike walks. CORRECT.

2. I walk faster than Mike walks. CORRECT.

3. I walk faster than Mike does. CORRECT.

4. A lion can run as fast as a tiger can run. CORRECT

5. A lion can run as fast as tiger can. CORRECT.

7. Fred will rent a canoe before Silvia does. CORRECT Source: Magoosh Blog.

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