It takes Matthew 3 minutes to dig a small hole for shrubs and 10 minutes to dig a large hole for trees.  How many hours will it take him to dig 30 small holes and 15 large holes?
It takes 3 minutes to dig a small hole and he needs to dig 30 small holes so it will take 3*30 = 
<gadget id="calculator">3*30</gadget>
<output>90</output>
90 minutes.
It takes 10 minutes to dig a large hole and he needs to dig 15 large holes so it will take him 15*10 = 
<gadget id="calculator">10*15</gadget>
<output>150</output>
150 minutes.
It will take 90 minutes to dig the small holes and 150 minutes to dig the large holes for a total of 90+150 = 
<gadget id="calculator">90+150</gadget>
<output>240</output>
240 minutes.
There are 60 minutes in 1 hour and he needs to dig for 240 minutes so that's 240/60 = 
<gadget id="calculator">240/60</gadget>
<output>4</output>
4 hours.

<result>4</result>