During the attendance check at university, my friend did the roll call for me.

He was asked to proxy for someone during the attendance check in class.

I looked for a cheap hotel to save on the cost of accommodation for my trip.

I looked for a cheap hotel to save on accommodation costs.

She is learning how to use pronouns.

I forgot to pay the bus fare.

The train fare is high, making my monthly expenses tough.

Who wrote this draft?

He is a professor of algebra.

This is a once-in-a-lifetime opportunity.