30 times the number A is equal to 40 times the number B. If the number A is 4, what is the number B?
甲数的30倍和乙数的40倍相等，如果甲数是4，那么乙数是多少？
<gadget id="calculator">30 / 40</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">4 * (3/4)</gadget>
<output>3</output>

<result>3</result>