"Whiter" or simply "more white" alone are both are acceptable. Examples:
This shirt is more white than the other one.
This shirt is whiter than the other one.
"Whiter" or simply "more white" alone are both are acceptable. Examples: This shirt is more white than the other one. This shirt is whiter than the other one.
I am, you are, he/she/it is, we are, they are.
The phrase "how don't I" is not grammatically correct. A more correct way to phrase it would be "why don't I."
No.
No, "most friendly" is not grammatically correct. The correct form would be "friendliest" when comparing three or more things.
Yes
The second one is more correct.
Yes, "is much more easily" is grammatically correct because it follows the correct order of adverbs (much, more, easily) when comparing multiple items or degrees in a sentence.
Yes, the phrase 'what they're doing' is grammatically correct. For example: What they're doing is wrong.
No, it is not. The "question word," why, should be at the beginning of the sentence. Why was she promoted?
Both "you and he" and "he and you" are grammatically correct, but "you and he" is more commonly used in English.
No. Us is the objective case, not the nominative case (we). It should be: We teens need more sleep. Or: We, as teens, need more sleep than others.