Bob drove for one and a half hours at 60/mph.  He then hit construction and drove for 2 hours at 45/mph. How many miles did Bob travel in those 3 and a half hours?
Bob drove for 1.5 hour * 60/mph = 
<gadget id="calculator">1.5*60</gadget>
<output>90</output>
90 miles.
Bod drove for 2 hour * 45/mph = 
<gadget id="calculator">2*45</gadget>
<output>90</output>
90 miles.
In total Bob drove 90 + 90 miles = 
<gadget id="calculator">90+90</gadget>
<output>180</output>
180 miles.

<result>180</result>