When a=5, b=4, c=3, what is the value of ac+bc.
当a=5，b=4，c=3时，ac+bc的值是多少．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<result>27</result>