The average of the two numbers A and B is 70, and the ratio of A and B is 2:5. What is the number of armor?
甲、乙两数的平均数是70，甲、乙两数的比是2：5．甲数是多少？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">70 * (2/7) * 2</gadget>
<output>40</output>

<result>40</result>