Jack is ordering custom baseball caps for him and his two best friends. Jack's head is 12 inches in circumference. Charlie's head is 9 inches more than half the circumference of Jack's head. Bill's head is 2/3 the circumference of Charlie's head. How many inches in circumference is Bill's head?
First find half the circumference of Jack's head: 12 inches / 2 = 
<gadget id="calculator">12/2</gadget>
<output>6</output>
6 inches.
Then find how big Charlie's head is: 6 inches + 9 inches = 
<gadget id="calculator">6+9</gadget>
<output>15</output>
15 inches.
Then find how big Bill's head is: 15 inches * 2/3 = 
<gadget id="calculator">15*2/3</gadget>
<output>10</output>
10 inches.

<result>10</result>