Verified answer

A mole of the alloy would have the apparent At Wt of the alloy:

(67.2× 6.022×10^23)/3.18×10^23) = 127.3

Let the fraction of Au (At Wt = 197.0) be x then the fraction of Pd (At Wt 106.4) = 1.00 - x. The apparent atomic weight is the weighted average of the At Wts:

197.0x + 106.4(1-x) = 127.3

197.0x - 106.4x = 127.3 - 106.4

90.6x = 20.9

x = 20.9/90.6 = 0.231 or 23.1 % Au, and 76.9% Pd