Xiao Ming's mother goes to the supermarket to buy 12 kilograms of apples and 8 kilograms of oranges. The apples cost a total of 42 yuan, and knowing that each kilogram of apples is 0.7 yuan more expensive than each kilogram of oranges, how much does it cost her mother to sell fruits in the supermarket?
小明的妈妈去超市买12千克苹果和8千克橘子，苹果共花42元，又知道苹果每千克比每千克橘子贵0.7元，妈妈去超市卖水果共花多少元？
<gadget id="calculator">42 / 12</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(7/2) - 0.7</gadget>
<output>2.8</output>

<gadget id="calculator">2.8 * 8</gadget>
<output>22.4</output>

<gadget id="calculator">22.4 + 42</gadget>
<output>64.4</output>

<result>64.4</result>