The water fee in a certain place is 0.45 yuan per degree when it does not exceed 10 degrees, and 0.8 yuan per degree when it exceeds 10 degrees. The Zhang family pays 3.30 yuan more than the Li family.
某地水费，不超过10度时，每度0.45元，超过10度时，每度0.8元，张家比李家多交水费3.30元，则张家交水费多少元．
<gadget id="calculator">0.45 * 10</gadget>
<output>4.5</output>

<gadget id="calculator">0.8 * 3</gadget>
<output>2.4</output>

<gadget id="calculator">4.5 + 2.4</gadget>
<output>6.9</output>

<result>6.9</result>