Teacher Li bought 4 simultaneous practice books and 3 oral calculation books for 59 yuan, and Mr. Zhang bought the same 2 simultaneous practice books and 3 oral calculation books for 43 yuan. How much is a book of simultaneous exercises.
李老师买来4本同步练习和3本口算书共用了59元，张老师买了同样的2本同步练习和3本口算共用了43元．一本同步练习多少元钱．
<gadget id="calculator">59 - 43</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>