Building one birdhouse requires 7 planks and 20 nails.  If 1 nail costs $0.05, and one plank costs $3, what is the cost, in dollars, to build 4 birdhouses?
The cost of the planks for one birdhouse is 7 * 3 = $
<gadget id="calculator">7*3</gadget>
<output>21</output>
21.
And the nails are a cost of 20 * 0.05 = $
<gadget id="calculator">20*0.05</gadget>
<output>1</output>
1 for each birdhouse.
So to build one birdhouse one will need 21 + 1 = $
<gadget id="calculator">21+1</gadget>
<output>22</output>
22.
So the cost of building 4 birdhouses is at 4 * 22 = $
<gadget id="calculator">4*22</gadget>
<output>88</output>
88.

<result>88</result>