To change the operation order of 196/28-21 to subtraction first, then division, how much should the formula be changed to?
要改变196/28-21的运算顺序为先算减法，再算除法，算式应该改为多少．
<gadget id="calculator">28 - 21</gadget>
<output>7</output>

<gadget id="calculator">196 / 7</gadget>
<output>28</output>

<result>28</result>