If Chester eats 3 eggs a day for 30 days and then increases it to 5 eggs a day for 30 days, how many dozens of eggs will Chester need for 60 days?
He starts off eating 3 eggs a day for 30 days for a total of 3*30 = 
<gadget id="calculator">3*30</gadget>
<output>90</output>
90 eggs.
Then he increases it to 5 eggs a day for 30 days for a total of 5*30 = 
<gadget id="calculator">5*30</gadget>
<output>150</output>
150 eggs.
All total he will eat 90+150 = 
<gadget id="calculator">90+150</gadget>
<output>240</output>
240 eggs.
There are 12 eggs in 1 dozen and he will 240 eggs which is 240/12 = 20 dozen eggs.

<result>20</result>