Which of the following situations involve opposite quantities combine to make 0? a. eva has a new piggy bank. she adds 7 quarters on wednesday and then adds another 5 quarters on friday. b. david made lemonade. he had 2 1⁄2 liters of water and used 5/2 liters for lemonade.

The correct answer is B.

He had 2 1/2 liters of water.  He used 5/2 liters of water to make lemonade.

To convert 5/2 to a mixed number, see how many times 2 goes into 5.  It goes twice, so 2 is the whole number.  The remainder after dividing 5 by 2 is 1, so this is the numerator of the fraction; this gives us 2 1/2. 

This means he started with 2 1/2 liters of water and used 2 1/2 liters of it.  This leaves him 0 liters of water.