The fruit bowl is 12 apples and 13 bananas the rest of the fruit is oranges what fraction of the fruit is oranges?
It depend upon how many oranges there are, which gives the total
number of pieces of fruit in the bowl.
Let the number of oranges be x, then the total number of fruit
is 12 + 13 + x = x +25
Thus the fraction of the fruit that is oranges is
number_of_oranges/total_number_of_fruit = x/(x+25)
If you do not know the number of oranges x, but do know the
total number of fruit in the bowl (call it t), then the number of
oranges = t - (12 + 23) = t - 25, giving the fraction of oranges as
(t-25)/t.
The above formulae give a general form of the fraction of the
fruit that are oranges; if you know the number of oranges, or the
total number of fruit, you can substitute for x or t in the above
formulae to get the fraction for the quantity you have as you have
not told us them.