A frog lays 800 eggs a year.  10 percent dry up, and 70 percent are eaten.  1/4 of the remaining eggs end up hatching, how many frogs hatch out of the 800?
Dried up:800(.10)=80 eggs
800(.70)=560 eggs.
Total left:800-80-560=
<gadget id="calculator">800-80-560</gadget>
<output>160</output>
160 eggs
160/4=
<gadget id="calculator">160/4</gadget>
<output>40</output>
40 eggs survive to hatch.

<result>40</result>