Together Felipe and Emilio needed a combined time of 7.5 years to build their homes. Felipe finished in half the time of Emilio. How many months did it take Felipe to build his house?
Let F = the number of years Felipe needed to build his house.
Emilio = 
<gadget id="calculator">2</gadget>
<output>2</output>
2F
3F = 7.5 years.
F = 
<gadget id="calculator">2.5</gadget>
<output>2.5</output>
2.5 years
2.5 years = 30 months.
It took Felipe 30 months to build his house.

<result>30</result>