It is known that a=2.5, b=5; then what is the value of 4a-b+2a.
已知a=2.5，b=5；则4a-b+2a的值是多少．
<gadget id="calculator">6 * 2.5</gadget>
<output>15</output>

<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<result>10</result>