Question

I am trying to decide if the infinitive phrase is used as a noun an adjective or an adverb.

To have a balanced diet, keep the food triangle in mind.

Is this an adverb that describes how to keep the food?

What about this one?
Fifty years ago, people didn't know to avoid "bad" cholesterol.

Is this a noun because it is a direct object

Answer 1

I agree with both of your answers.

Answer 2

I am stuck on this one.

Would you like to read this detective novel?

I am torn between adjective and noun. Noun because it is a direct object or adjective because it describes you?

And this one.
My grandmother taught me to make lentil soup.

I am thinking adverb because it describes what she taught or noun because it is a direct object?

Answer 3

Both are nouns, used as direct objects.