The average of the three numbers A, B and C is 19, the ratio of A and B is 3:4, C is 3 less than A, what is A
甲、乙、丙三个数的平均数是19，甲、乙两数的比是3：4，丙比甲少3，甲是多少
<gadget id="calculator">19 * 3</gadget>
<output>57</output>

<gadget id="calculator">57 + 3</gadget>
<output>60</output>

<gadget id="calculator">3 + 4 + 3</gadget>
<output>10</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">60 * (3/10)</gadget>
<output>18</output>

<result>18</result>