There are 105 students in Class A and Class B. The ratio of boys and girls in Class A is 4:3, and the ratio of boys and girls in Class B is 5:3. How many boys are there in Class A?
甲乙两班共有105人，甲班男女生之比是4：3，乙班男女之比是5：3，则甲班有男生多少人．
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">49 * (4/7)</gadget>
<output>28</output>

<result>28</result>