witch is the better 10.00 for 17 apples or 17.00 for 20 oranges

If, "by better", you mean the cheapest per item:

Apples:    $10.00 / 17  =  $0.59  per apple.        <---  cheapest per item!

Oranges:  $17.00 / 20  =  $0.85  per orange.