Decimals theory question

Hi all,

I was recently watching a video on Youtube that referred to a concept I hadn’t seen before, and can’t find any more information on, I was hoping someone could assist me.

It had a QC styled question and asked which is bigger: the number of tenths equal to 1.8 or the number of hundreds equal to 1.7. Any help would be greatly appreciated.

Thanks!

is answer A???

I’m not sure, I don’t know how to solve