Give the step-by-step reasoning process and then the final answer. 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?
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The total number of light bulbs in the 20 lamps is 20 * 7 = 140. If 1 / 4 of the 20 lamps have burnt - out light bulbs, there are 1 / 4 * 20 = 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 = 10. The number of working light bulbs is 140 - 10 = 130.
The final answer: 130.
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