Teacher Wang goes to buy school aids. If he buys 8 school aids with a unit price of 18.5 yuan, it is not enough. If he buys 12.5 school aids, he can buy 11 pieces, and there is still a surplus; After using up the money, what is the approximate unit price of the learning tools Mr. Wang bought?
王老师去买学具，如果买8件单价18.5元的学具，尚且不足，如果买单价12.5元的学具，可以买11件，尚有剩余；王老师最终买了10件学具，恰好用完所带的钱，王老师所买的学具的单价大约是多少元？
<gadget id="calculator">140 / 10</gadget>
<output>14</output>

<result>14</result>