david gave 1/5 of his oranges to his brother. his brother got 15 oranges. he gave his friend donny 1/3 of the remainder.

a) how much oranges did david have originally?
b) how many did donny get?
c) how many oranges was david left with?

clearly David had 75 oranges.

The rest then can be easily found.

To find the answers to these questions, we can break down the problem step by step. Let's start with question a) and find out how many oranges David had originally.

a) To determine how many oranges David had originally, we need to calculate the portion that he gave to his brother and the portion that he has left.

Let's assume the variable "x" represents the number of oranges David had originally.

David gave 1/5 of his oranges to his brother, so he has (1 - 1/5) = 4/5 of the original amount left.

We know that 4/5 of the oranges is equal to 15, so we can set up the following equation:

(4/5) * x = 15

To solve the equation, we can multiply both sides by 5/4 to isolate "x":

x = 15 * (5/4)
x = 18.75

Therefore, David originally had 18.75 oranges.

b) Now, let's calculate how many oranges Donny received.

David gave Donny 1/3 of the remainder after giving his brother the oranges. Let's calculate the remainder first.

The remainder is (4/5) * 18.75 = 15

David gave Donny 1/3 of the remainder, so we can calculate it as follows:

(1/3) * 15 = 5

Donny received 5 oranges.

c) Finally, let's calculate how many oranges David was left with.

David gave away a total of 15 oranges (to his brother and Donny). Therefore, he was left with:

18.75 - 15 = 3.75

David was left with 3.75 oranges.

In summary:
a) David originally had 18.75 oranges.
b) Donny received 5 oranges.
c) David was left with 3.75 oranges.