Rick has just celebrated his 15th birthday. His oldest brother is twice his age, and his middle brother is a third of the oldest brother’s age. The smallest brother is half the middle brother’s age. If the youngest brother is 2 years younger than the smallest brother, how old, in years, is the youngest brother?
Rick's oldest brother is 15 years * 2 = 
<gadget id="calculator">15*2</gadget>
<output>30</output>
30 years old.
This means the middle brother is 30 years / 3 = 
<gadget id="calculator">30/3</gadget>
<output>10</output>
10 years old.
The smallest brother is therefore 10 years / 2 = 
<gadget id="calculator">10/2</gadget>
<output>5</output>
5 years old.
So the youngest brother is 5 years - 2 years = 
<gadget id="calculator">5-2</gadget>
<output>3</output>
3 years old.

<result>3</result>