Only 16 households in Xingfu Community used natural gas the year before last. Last year, the number of households using natural gas was four times that of the previous year, and this year, the number of households using natural gas increased by 20 compared with last year. How many households use natural gas this year?
幸福社区前年只有16户使用天然气．去年使用天然气的户数是前年的4倍，今年使用天然气的又比去年增加了20户．今年使用天然气的一共有多少户？
<gadget id="calculator">16 * 4</gadget>
<output>64</output>

<gadget id="calculator">64 + 20</gadget>
<output>84</output>

<result>84</result>