The number A is a, and the number B is less than (7/8) b of the number A. What is the formula for the number B?
甲数是a，乙数比甲数的(7/8)少b，表示乙数的式子是多少．
<gadget id="calculator">7 / 8</gadget>
<output>7/8 = around 0.875</output>

<result>7/8 = around 0.875</result>