Try this:
1. sum of numbers is x+y=67, the difference between them is x-y=11
2. it is possible to make up and resolve the system:
Answer: 5 brownies
Step-by-step explanation:
cookies = 5 x $0.50 = $2.5
$15 - $2.5 = $12.5
$12.5 divided by $2.25 = $5.555
so at the most ella can buy 5 brownies if she buys 5 cookies
The answer to your question is nine