Given that x=0.5, y=1.3 find the value of 3y-4x.
已知x=0.5，y=1.3求3y-4x的值．
<gadget id="calculator">3 * 1.3</gadget>
<output>3.9</output>

<gadget id="calculator">4 * 0.5</gadget>
<output>2</output>

<gadget id="calculator">3.9 - 2</gadget>
<output>1.9</output>

<result>1.9</result>