Question 484132
This is obviously too easy as a math problem.
It's more likely a riddle, and with a flaw at that.
If "row" is a well defined quantity, Answer=18.75.
The "gotcha" is that a fractional row is still just a row, so Answer=20.
But if this is the case, then there is no such thing as a 1/4 row!
So the riddle statement has its own Gotcha!
I first saw this decades ago with the excellent riddle wherein the 3 fields contained interger number of haystacks.  Farmer puts them all together and how many does he have?  Just 1, very nice.  Then I saw someone "improve" the riddle to fractinal haystacks!  If size doesn't count, you can't have fractions!