It is known that a and b are prime numbers (a>b), ab represents the product of a and b, if a+ab+b=55, then what is the value of ab.
已知a，b为质数(a＞b)，ab表示a与b的乘积，若a+ab+b=55，那么a-b的值是多少．
<gadget id="calculator">13 - 3</gadget>
<output>10</output>

<result>10</result>