Given that x=5 is the solution of the equation 3x-2a=7, what is the value of a?
已知x=5是方程3x-2a=7的解，则a的值为多少．
<gadget id="calculator">15 - 7</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<result>4</result>