<span>21 1/3 children will be served with the amount of 4 gallons of cider.</span>
Jace bought 4 cookies and 2 brownies from the bakery.
Let x represent the number of cookies and y represent the number of brownies.
Since he bought $9 worth of cookies and brownies. Each cookie costs $0.75 and each brownie costs $3. hence:
0.75x + 3y = 9 (1)
Also, he bought twice as many cookies as brownies, hence:
x = 2y
x - 2y = 0 (2)
Solving equation 1 and 2 simultaneously gives x = 4, y = 2
Hence Jace bought 4 cookies and 2 brownies from the bakery.
Her brother is 9.
Because she is 3 years older than half his age, subtract 3 - 21. This gives 18. Then divide 18 / 2. This gives 9.
