The ratio of the numbers A and B is 3:5, the number B minus the number A is 21, what is the number B?
甲、乙两数的比是3：5，乙数减甲数得21，乙数是多少？
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">21 / 2</gadget>
<output>21/2 = around 10.5</output>

<gadget id="calculator">(21/2) * 5</gadget>
<output>105/2 = around 52.5</output>

<result>105/2 = around 52.5</result>