There are four numbers A, B, C, and D. The average number of A and B is 34.3; the average number of B and C is 19.85; the average number of A and C is 35.75; the average number of B and D is 20. What is the largest of these four numbers?
有甲、乙、丙、丁四个数，甲、乙的平均数为34.3；乙、丙的平均数为19.85；甲、丙的平均数为35.75；乙、丁的平均数为20．则这四个数中最大的数是多少？
<result>50.2</result>