Reyna had 20 lamps with seven light bulbs in each lamp. If 1/4 of them have 2 burnt-out light bulbs each, how many light bulbs are working?
The total number of light bulbs in the 20 lamps is 20*7 = 
<gadget id="calculator">20*7</gadget>
<output>140</output>
140.
If 1/4 of the 20 lamps have burnt-out light bulbs, there are 1/4*20 = 
<gadget id="calculator">1/4*20</gadget>
<output>5</output>
5 lamps with burn out light bulbs.
Since each of the 5 lamps has 2 burnt-out light bulbs, the number of burn out light bulbs is 2*5 = 
<gadget id="calculator">2*5</gadget>
<output>10</output>
10.
The number of working light bulbs is 140 -10 = 
<gadget id="calculator">140-10</gadget>
<output>130</output>
130.

<result>130</result>