The first step is to find a common denominator. One fifth is equal to two tenths, so seven tenths minus two tenths is equal to five tenths - or one half.

No, seven tenths 7/10 is bigger than three tenths 3/10. If you had a pie cut into ten slices, would you rather have 7 pieces or 3? If you had 7 of those pieces, or 7/10 seven tenths, you'd have more of the pie than 3/10.