The power supply company stipulates that: the monthly electricity consumption does not exceed 100 kWh (including 100 kWh), and the charge is 0.5 yuan per kwh; the monthly electricity consumption exceeds 100 kwh, and the excess part is charged at 0.6 yuan per kwh. Xiaoming's family paid 68 yuan for electricity in May. How many kWh did they use?
供电公司规定：每月用电不超过100千瓦时(含100千瓦时)，每千瓦时按0.5元收费；每月用电超过100千瓦时，超过的部分按每千瓦时0.6元收费．小明家5月份付电费68元，用电多少千瓦时？
<gadget id="calculator">0.5 * 100</gadget>
<output>50</output>

<gadget id="calculator">68 - 50</gadget>
<output>18</output>

<gadget id="calculator">18 / 0.6</gadget>
<output>30</output>

<gadget id="calculator">30 + 100</gadget>
<output>130</output>

<result>130</result>