The compound A2XA2X is 30.6 %% AA by mass. What mass of the compound contains 67.6 gg AA?

1) First you need to multiply 67.6 by 2, because A₂X has to atoms of A. So:
67.6 × 2 = 135.2
135.2 g is 30.6% of the mass of the compound. So:
135.2 ----- 30.6%
x ----- 100%
x = 441.8 g
Answer: 442g