Answer
Atomic mass of Y in amu = 103.26 amu
Work Step by Step
Atomic mass of X in amu = 33.42 amu
Atomic mass of X in gram = 33.42 g
Given 27.22 g of X combine with 84.10 g of Y to form XY.
Therefore mass of Y required to combine with 33.42 g X =
$ (84.10 \times 33.42) \div 27.22 = 103.26 g$
Atomic mass of Y in amu = 103.26 amu