To solve this problem, we need to determine the value of x, which represents the percentage of Jack's head circumference that Charlie's head circumference is.
Let's break down the information given:
Jack's head circumference: 12 inches
Charlie's head circumference: x% * 12 inches + 9 inches
Bill's head circumference: 2/3 * (x% * 12 inches + 9 inches)
Bill's head circumference: 10 inches
We can set up the equation as follows:
2/3 * (x% * 12 inches + 9 inches) = 10 inches
Let's simplify and solve for x:
2/3 * (x/100 * 12 inches + 9 inches) = 10 inches
Multiply both sides of the equation by 3/2 to get rid of the fraction:
(x/100 * 12 inches + 9 inches) = 10 inches * 3/2
x/100 * 12 inches + 9 inches = 15 inches
Subtract 9 inches from both sides of the equation:
x/100 * 12 inches = 15 inches - 9 inches
x/100 * 12 inches = 6 inches
To isolate x, we multiply both sides of the equation by 100/12:
(x/100 * 12 inches) * (100/12) = 6 inches * (100/12)
x = 600/12
x = 50
The value of x is 50.
#### 50
The answer is: 50
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
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 x% the circumference of Jack's head. Bill's head is 2/3 the circumference of Charlie's head. Bill's head is 10 inches in circumference.

### Answer:
