Solve the equation: 0.8(x-4)=7.2.
解方程：0.8(x-4)=7.2．
<gadget id="calculator">0.8 * 4</gadget>
<output>3.2</output>

<gadget id="calculator">3.2 + 7.2</gadget>
<output>10.4</output>

<gadget id="calculator">10.4 / 0.8</gadget>
<output>13</output>

<result>13</result>