For every white duck at the lake there are 5 fish.  For every black duck there are 10 fish and for every multicolor duck there are 12 fish.  Currently there are 3 white ducks, 7 black ducks and 6 multicolored ducks.  How many fish are in the lake?
For every white duck there are 5 fish and there are 3 white ducks for a total of 5*3 = 
<gadget id="calculator">5*3</gadget>
<output>15</output>
15 fish.
For every black duck there are 10 fish and there are 7 black ducks for a total of 10*7 = 
<gadget id="calculator">10*7</gadget>
<output>70</output>
70 fish.
For every multicolored duck there are 12 fish and there are 6 multicolored ducks for a total of 12*6 = 
<gadget id="calculator">12*6</gadget>
<output>72</output>
72 fish.
All total there are 15+70+72 = 
<gadget id="calculator">15+70+72</gadget>
<output>157</output>
157 fish in the lake.

<result>157</result>