Answer: 3 balloons
Step-by-step explanation:
The ratio would be pink balloons to total balloons (aka pink/total), so 5 to 20 (aka 5/20). This simplifies to 1/4. If the new total is 12, and x represents pin balloons, then you can do 1/4=x/12. By cross multiplying, you get 12=4x. Divide both sides by 4 and x would equal 3. Therefore, the party store should expect to sell 3 pink balloons.