Last month, Dad's mobile phone bill was 248 yuan, which was 13 yuan less than twice the mother's mobile phone bill. How much was your mother's mobile phone bill last month? (solution by equation)
上个月爸爸的手机话费是248元，比妈妈手机话费的2倍少13元．上个月妈妈的手机话费是多少元？(用方程解)
<gadget id="calculator">248 + 13</gadget>
<output>261</output>

<gadget id="calculator">261 / 2</gadget>
<output>261/2 = around 130.5</output>

<result>261/2 = around 130.5</result>