I can place the palms of my hands on the floor without bending my knees.

The verb 'help' takes to-infinitives and bare infinitives but bare infinitives are said to be the most common in casual text; as also used in this example sentence.

Saying they could not support both a wife and an airplane, the two brothers therefore spent their lives as bachelors.

You can't have your cake and eat it too.

A common theme underlies both perspectives.

I don't like either of them.

I do not like both of them.

They are both good.

You can't have your cake and eat it too.

Both parents and teachers educate their children.

She is capable of teaching both English and French.

She can speak both English and German.

I haven't read either of her novels.

I haven't read both of her novels.

They speak English or French or both.

Both of them were not present at the meeting.

I doubt whether he will win both races.

He can speak both Japanese and English with facility.

He can speak both English and German.

He doesn't speak either English or French.