When a is equal to what, the solution of ax-18=6 is x=15.
当a等于多少时，ax-18=6的解是x=15．
<gadget id="calculator">6 + 18</gadget>
<output>24</output>

<gadget id="calculator">24 / 15</gadget>
<output>8/5 = around 1.6</output>

<result>8/5 = around 1.6</result>